<PAGE>   1
                                                                   Exhibit 10.15

                         [LETTERHEAD OF PNC BANK, N.A.]
March 9, 1998
                                                                         PNCBANK
Mr. David Lauber
Party City Corporation
400 Commons Way
Rockaway, NJ  07866

Dear Mr. Lauber:

Party City Corporation (the "Company") has requested that PNC Bank, National
Association ("PNC Bank" or the Agent") underwrite up to $60,000,000 of credit
facilities (the "Financing") for general corporate purposes including the
refinancing of existing PNC Bank indebtedness, providing for store expansion,
and the acquisitions of franchise stores.

We are pleased to inform you that PNC Bank commits to provide $60,000,000 of the
Financing described in the attached Summary of Terms and Conditions (the
"Summary"), subject to the terms and conditions referred to in this letter and
the Summary. The Summary includes a description of the principal terms of the
proposed credit facilities connected with the Financing, and is intended as a
framework for the documentation and as a basis for further discussion of the
Financing's terms, as appropriate. The Financing will be documented in a
definitive credit agreement (the "Credit Agreement") and other agreements,
instruments, certificates, and documents called for by the Credit Agreement or
which PNC BANK may otherwise require (collectively, the "Credit Documents"), to
be delivered at the closing of the Financing (the "Closing"). The terms of the
Credit Documents shall prevail over the terms of this letter.

PNC Bank's obligations are conditioned on the execution and delivery of the
Credit Documents to PNC BANK in form and content satisfactory to PNC BANK.
Because not all of the terms can be set forth in the Summary, a failure by the
Bank or the Company to agree on the definitive terms of the Credit Documents
will not constitute a breach of this commitment. This letter is also subject to
acceptance by the Company as provided below and the statutory and other
requirements under which PNC BANK is governed.

In addition to the terms and conditions set forth in the Summary, PNC Bank's
commitment to provide the proposed Financing is further subject to: (i) there
being no material adverse change in the financial condition, business,
operations, properties, or prospects of the Company from the information
provided to PNC BANK in its due diligence process; and (ii) the non-occurrence
of any material adverse change in the loan
<PAGE>   2

Party City Corporation
March 9, 1998
Page 2


syndication or capital market conditions generally, which would affect the
syndication efforts by PNC BANK in its capacity as Agent in respect of any
portion of the Financing.

This letter is issued in reliance on the information provided to PNC BANK by the
Company in connection with the Company's request for the Financing and the
information in any supporting document and material. PNC Bank may terminate this
commitment if there is any material misrepresentation or material inaccuracy in
the information or any failure to include material information with the request.

By executing this letter, the Company agrees to indemnify and hold harmless PNC
Bank or any affiliate thereof and any assignees or participants thereof and
their respective officers, directors, employees, affiliates and agents from and
against any and all losses, claims, damages, liabilities, costs and expenses
(including without limitation reasonable fees and expenses of counsel) which may
be incurred by any of them in connection with any investigation, litigation or
other proceeding arising in connection with the Financing, other than for their
own gross negligence or willful misconduct. The Company's obligations hereunder
shall be in addition to any other liability it may otherwise have.

The Company agrees to pay the fees set forth in the Summary. PNC BANK shall be
reimbursed from time to time by the Company upon request for all reasonable
out-of-pocket expenses (including without limitation reasonable fees and
expenses of counsel) which it may incur in the negotiation, preparation, due
diligence, execution and delivery of this letter, the Credit Documents and other
documentation and any assignment or participation of its interests herein,
regardless of whether the transaction contemplated by this letter is completed
or the Credit Documents are signed.

The terms contained in this letter and the Summary are confidential and, except
for disclosure to the Company's board of directors, officers and employees,
professional advisors retained by the Company in connection with this
transaction, or as may be required by law, may not be disclosed in whole or in
part to any other person or entity without PNC Bank's prior written consent.
This letter is solely for the benefit of the Company and no other person or
entity shall obtain any rights hereunder or be entitled to rely or claim
reliance upon the terms and conditions hereof.

This commitment letter may not be assigned by the Company and no rights of the
Company hereunder may be transferred without the prior written consent of PNC
Bank. PNC BANK may elect to (a) assign a portion of its rights and obligations
hereunder so that the assignee may become a party to the Credit Agreement and
(b) arrange for the sale of participation interests in its commitment hereunder
and/or loans made by it as contemplated hereby. In the event of any assignment
referred to in (a) above, the assignor shall be released of all obligations
assumed by the assignee.
<PAGE>   3

Party City Corporation
March 9, 1998
Page 3


This commitment letter shall be governed by and construed in accordance with the
laws of the State of New Jersey.

PNC Bank and any assignees or participants will in no event be responsible or
liable for any consequential damages that may be incurred or alleged by any
person as a result of this letter. No modification or waiver of any of the terms
and conditions of this letter will be valid and binding unless agreed to in
writing by PNC BANK. When accepted, this letter constitutes the entire agreement
between PNC BANK and the Company concerning the Financing and replaces all prior
understandings, statements and negotiations.

This commitment letter will expire on March 20, 1998, unless on or before that
date the Company signs and returns the enclosed copy of this letter along with
the Commitment Fee stated below. Once accepted, PNC Bank's obligations under
this letter will expire automatically and without further liability to PNC BANK
on May 20, 1998 if the Financing has not closed on or before that date. Both of
these expiration dates may be extended only if agreed to in writing by PNC Bank.

If the foregoing accurately sets forth our understanding, please indicate your
acceptance hereof by signing the enclosed copy of this letter and returning it
to us with payment of our commitment fee in the amount of $100,000. This
Commitment Fee along with the previously submitted deposit of $30,000 is
considered non-refundable whether or not the transaction closes. These fees
shall be applied to the underwriting fee due at closing. We are pleased to have
this opportunity and very much look forward to working with you.

Sincerely,

PNC Bank, National Association


David Krietzberg
Vice President

Agreed to and accepted:

Party City Corporation

By: /s/ David Lauber
   ----------------------
Date: 3/18/98

cc: Steven Mandell
<PAGE>   4

Party City Corporation
March 9, 1998
Page 4


                         Summary of Terms and Conditions
                              $60,000,000 Revolver
                                  March 9, 1998

Borrower:               Party City Corporation (the "Company").

Agent:                  PNC Bank, National Association ("PNC Bank or Agent")

Banks:                  The Agent and lending institution(s) acceptable to the
                        Company and the Agent providing a portion of the Credit
                        Facilities described below (the "Banks").

Credit Facility:        Subject to acceptable documentation, PNC BANK
                        commits to provide up to $60,000,000 of a $60,000,000
                        three-year revolving credit facility (the "Credit
                        Facility").

Purpose:                Refinance existing indebtedness, provide for store
                        expansion, acquisitions of existing Party City
                        franchised stores, and general corporate purposes.

Maturity:               Three years from closing.

Repayment:              At maturity. Until maturity, the Company may borrow,
                        repay and reborrow an amount not to exceed $60,000,000.

Interest Rate on the
Credit Facility:        The Borrower will have the option of Interest Rates tied
                        to the Base Rate or LIBOR. Interest Rates will be tiered
                        based on the Company's Fixed Charge Coverage Ratio
                        according to the attached Pricing Grid. The initial
                        measurement date shall be as of 3/31/98.

                        The Fixed Charge Coverage Ratio is defined as the ratio
                        of EBITR to Fixed Charges.

                        EBITR is defined as net income (before extraordinary
                        income) plus income tax expense, interest expense,
<PAGE>   5

Party City Corporation
March 9, 1998
Page 5


                        and rent expense, all measured as of the end of each
                        quarter for the previous four quarters.

                        Fixed Charges is defined as the sum of interest expense
                        and rent expense, both measured as of the end of each
                        quarter for the previous four quarters.

                        The Base Rate is the higher of PNC Bank's Prime rate as
                        defined in the documentation or the Federal Funds rate
                        plus One Half of One Percent (1/2%).

                        Interest on Base Rate borrowings is calculated on an
                        actual/365 or 366 day basis and is payable quarterly.

                        Interest on LIBOR borrowings is calculated on an
                        actual/360 day basis and is payable the earlier of
                        quarterly or on the last day of each interest period.
                        LIBOR advances will be available for periods of 1,2,3 or
                        6 months. LIBOR pricing will be adjusted for any
                        statutory reserves.

                        The Company may have no more than five borrowing
                        tranches, including the Base Rate tranche, at any one
                        time.

                        Subsequent to an Event of Default which continues beyond
                        any applicable cure period, outstandings shall bear
                        interest at Two Percent (2.00%) over the rate of
                        interest applicable under the Base Rate pricing option.

Underwriting Fee:       75 basis points ($450,000) payable to the Agent at
                        closing, less any deposits and commitment fees already
                        paid by the Company to the Agent for this specific
                        transaction.

Agent's Fee:            $15,000 per annum payable to the Agent, assuming
                        three Banks as lenders. The Agent's Fee will be
                        increased by $5,000 per annum for each additional Bank
                        that becomes a lender.

Yield Protection:       The Company shall pay the Banks such additional amounts
                        as will compensate the Banks in the event
<PAGE>   6

Party City Corporation
March 9, 1998
Page 6


                        applicable law, change in law, or in interpretation of
                        law, subjects the Banks to reserve requirements, capital
                        requirements, taxes (except for taxes on the overall net
                        income of the Banks) or other charges which increase the
                        cost or reduce the yield to the Banks, under customary
                        yield protection provisions.

Expenses:               Reasonable out-of-pocket expenses incurred by Agent
                        shall be for the account of the Company. These include
                        fees and expenses of the Agent's legal counsel.

Collateral:             First priority perfected lien on all receivables,
                        including franchise royalties and fees, inventory,
                        equipment, furniture, fixtures, improvements and
                        intangibles, as well as the right to obtain a mortgage,
                        or such other security interest in any real property of
                        the Borrower, as Agent in its discretion deems necessary
                        in the future.

Mandatory Commitment
Reductions:             Mandatory commitment reductions will be required upon
                        any material sale of assets as defined in the
                        documentation. Prepayments will not be required,
                        however, if after-tax proceeds from asset sales totaling
                        up to $500,000 are used to acquire substitute assets in
                        the ordinary course of business and such assets are
                        pledged to the Banks within thirty (30) days.

Interest Rate
Protection:             Minimum Twenty Five Percent (25%) of outstandings under
                        the Credit Facility to be hedged, as defined in the
                        documentation, at all times, which shall be secured by
                        the Collateral as defined herein.

Representations and
Warranties:             The documentation shall require typical representations
                        and warranties as to matters expected in a Credit
                        Facility of this nature including, but not limited to:

                        a. Organization and qualification.

                        b. Capitalization and ownership.
<PAGE>   7

Party City Corporation
March 9, 1998
Page 7


                        c. Subsidiaries.

                        d. Power and authority.

                        e. Validity, binding effect and enforceability.

                        f. No conflict.

                        g. Litigation.

                        h. Title to properties.

                        i. Financial statements; no material adverse change.

                        j. Margin stock.

                        k. Full disclosure.

                        l. Taxes.

                        m. Consents and approvals.

                        n. No Event of Default; compliance with contracts and
                           instruments.

                        o. Patents, trademarks, copyrights, licenses.

                        p. Security interests.

                        q. Mortgage liens.

                        r. Status of pledged collateral.

                        s. Insurance.

                        t. Compliance with laws.

                        u. Material contracts.

                        v. Investment companies.
<PAGE>   8

Party City Corporation
March 9, 1998
Page 8


                        w. Plans and benefit arrangements.

                        x. Employment matters.

                        y. Environmental matters.

                        z. Senior debt status.

                        aa. Year 2000 Compliance

                        Other Representations and Warranties as appropriate.

Conditions Precedent
to Closing:             Receipt by Agent of the following, in form and substance
                        satisfactory to the Agent and the Banks:

                        a.    Closing certificate as to accuracy of
                              Representations and Warranties, compliance with
                              covenants and absence of Event of Default or
                              Potential Event of Default.

                        b.    Certified resolutions, incumbency certificate and
                              corporate documents.

                        c.    Delivery of all definitive financing documents and
                              evidence of filing of all collateral documents.

                        d.    Opinion(s) of counsel.

                        e.    Receipt of audited December 31, 1997 financial
                              statements by independent certified public
                              accountants satisfactory to PNC BANK.

                        f.    Receipt of management's financial projections
                              prepared for fiscal year 1998 on a quarterly
                              basis.

                        g.    No material adverse change.

                        h.    No material litigation.
<PAGE>   9

Party City Corporation
March 9, 1998
Page 9


                        i.    Evidence of required insurance.

                        j.    Payment of all fees and expenses.

                        k.    A schedule detailing as to all Company locations:
                              store name, store number, address, and square
                              footage. A copy of all leases for all
                              Company-owned stores. A schedule of leases that do
                              not contain Landlord Waivers, the total number of
                              which shall not exceed the number of leases that
                              have been previously waived in writing by PNC
                              BANK.

                        l.    The Company and PNC BANK shall have agreed to a
                              modification of the standard Landlord Waiver
                              language contained in all future Company-owned
                              stores leases.

                        Other Conditions Precedent to Lending as appropriate in
                        the discretion of PNC BANK.

Affirmative Covenants   The Company will:

            o     Provide within 45 days after each month end, monthly unaudited
                  financial statements of month end, along with individual
                  Company-owned store profit and loss reports for the
                  year-to-date period then ending, depicting actual, budget,
                  variance analysis, and comparisons to the same period the
                  prior year and a Certificate of Compliance from the CEO,
                  President or CFO.

            o     Provide within 45 days after each of the first three fiscal
                  quarters, quarterly unaudited financial statements and 10Q's,
                  along with a Certificate of Compliance from the CEO, President
                  or CFO. In the event that a subsidiary is created, then
                  consolidated and consolidating financial reporting will be
                  required.

            o     Provide within 90 days after each fiscal year end, audited
                  financial statements and 10K along with (i) a report of an
                  independent Certified Public Accountant satisfactory to the
                  Agent, (ii) any management letters of such accountants
                  addressed to the Company, (iii) a Certificate of Compliance
                  from the CEO, President or CFO and (iv) Annual Report and
                  Shareholder Proxy Statements. In the event that a subsidiary
                  is created, then consolidated and consolidating financial
                  reporting will be required.
<PAGE>   10

Party City Corporation
March 9, 1998
Page 10


            o     Provide within fifteen (15)days from the date of possession of
                  new Company-owned stores, a listing with detailed address
                  information and a copy of the associated lease agreement,
                  together with UCC-1 form or forms executed by the Borrower
                  suitable for recording in the affected jurisdiction(s).

            o     Provide prior to each year end, a three year projection of
                  financial statements showing detailed income statements,
                  balance sheets, and cash flow statements by month for the
                  first year and by quarter for each of the subsequent two
                  years. The first year cash flow should include a detailed
                  schedule of cash receipts and disbursements and show the
                  beginning and month end borrowings. In addition, the Company
                  will supply a detailed budget showing individual store Profit
                  And Loss Reports forecasted for the upcoming year including,
                  but not limited to, expected store openings, and capital
                  expenditures.

            o     All reports prepared by outside accountants shall be
                  accompanied by a writing evidencing the Company's knowledge
                  that such reports are being supplied to Agent by the
                  accountants and that Agent and the Banks are intended to rely
                  upon such reports.

                        Other Affirmative Covenants as deemed appropriate in the
                        Agent's discretion.

Negative Covenants:     The Company will not breach the following required
                        ratios or covenants:


                        Liquidity Ratio - The ratio of the Company's cash,
                        accounts receivable and inventory to outstandings under
                        the Credit Facility shall not be less than the
                        following:

<TABLE>
<CAPTION>
                                               1998-2000
                                               ---------
<S>                                            <C>
                               Jan.- Apr.      1.50:1.00
                               May-Aug.        1.40:1.00
                               Sept.-Dec.      1.50:1.00
</TABLE>

                        b.    Leverage - The Company's ratio of Total
                              Indebtedness to EBITDA shall not exceed the
                              following:
<PAGE>   11

Party City Corporation
March 9, 1998
Page 11


<TABLE>
<S>                                  <C>               <C>
                                     1st Quarter       2.50:1.00
                                     2nd Quarter       2.50:1.00
                                     3rd Quarter       3.25:1.00
                                     4th Quarter       1.50:1.00
</TABLE>

                              If Leverage exceeds 2.50:1 as of the end of the
                              3rd Quarter, the Leverage covenant shall be
                              measured again as of 10/31/XX and shall not exceed
                              1.50:1. For purposes of this test only, Total
                              Indebtedness shall be as of 11/10/XX while EBITDA
                              shall represent the twelve months ended 10/31/XX.

                              Total Indebtedness is defined as the Company's
                              consolidated long and short term indebtedness for
                              borrowed money, capital leases, guarantees and
                              letters of credit, all measured as of the end of
                              each quarter.

                              EBITDA is defined as net income (before
                              extraordinary income), plus income tax expense,
                              interest expense, depreciation and amortization
                              expense, all measured as of the end of each
                              quarter for the previous four quarters.

                        c.    Fixed Charge Coverage Ratio - As of the end of
                              each fiscal quarter, the Company's ratio of EBITR
                              to Fixed Charges shall not be less than the
                              following:

<TABLE>
<S>                                  <C>               <C>
                                     1st Quarter       1.35:1
                                     2nd Quarter       1.35:1
                                     3rd Quarter       1.20:1
                                     4th Quarter       1.50*
</TABLE>

                                     * Reduced to 1.40:1 for the fourth quarter
                                     1999 and 2000.

                              EBITR is defined as net income
                              (before extraordinary income) plus income tax
                              expense, interest expense, and rent expense, all
                              measured
<PAGE>   12

Party City Corporation
March 9, 1998
Page 12


                              as of the end of each quarter for the previous
                              four quarters.

                              Fixed Charges is defined as the sum of interest
                              expense and rent expense, both measured as of the
                              end of each quarter for the previous four
                              quarters.

                        d.    Tangible Net Worth - The Company's tangible net
                              worth shall not be less than $30,000,000 at
                              12/31/97 plus 50% of annual net income plus 100%
                              of the net proceeds of any new equity issuances by
                              the Company. This covenant shall be tested on an
                              annual basis.

                        e.    Minimum Net Worth and/or Maximum Debt to Net Worth
                              Such a covenant, to be tested on a quarterly
                              basis, will be negotiated for inclusion in the
                              definitive documentation.

                        f.    Capital Expenditures - Capital expenditures,
                              including capitalized leases but excluding
                              acquisition costs of intangible assets, shall not
                              exceed the amounts shown opposite each period
                              below.

<TABLE>
<CAPTION>
                                     FYE         Amount
                                     ---         ------
<S>                                  <C>         <C>
                                     1998        $26,000,000
                                     1999        $26,000,000
                                     2000        $26,000,000
</TABLE>

                        g.    Limitation on sale of assets.

                        h.    Restriction on loans, advances and investments.

                        i.    Limitation on additional indebtedness, liens and
                              leases.

                        j.    Prohibition against cash distributions to
                              shareholders.

                        k.    Prohibition on change of business.
<PAGE>   13

Party City Corporation
March 9, 1998
Page 13


                        l.    Prohibition on change of control.

                        m.    No Mergers or acquisitions permitted, except under
                              the following conditions: (1) the Company is the
                              surviving entity, (2) the Company is in proforma
                              compliance with all covenants after taking the
                              acquisition into account, (3) the entity being
                              acquired is an existing Party City franchisee, (4)
                              purchase multiple and structure is consistent with
                              the Company's stated parameters and prior
                              acquisitions, and (5) cash consideration for
                              acquisitions limited to $12,500,000 in the
                              aggregate per fiscal year and limited to
                              $30,000,000 in aggregate during the term of the
                              Facility.

                        n.    The Company shall not execute new store leases
                              that do not contain a Landlord Waiver in language
                              that conforms to the new Standard Waiver language
                              to be formalized or that is not otherwise
                              satisfactory to PNC BANK for all Company-owned
                              stores without PNC BANK's prior written consent.

                        Other Negative Covenants as appropriate.

Events of Default:      Events of Default typical to a transaction of this
                        nature will be required, to include, but not be limited
                        to:

                        a.    Payment default.

                        b.    Breach of Representations or Warranties.

                        c.    Violation of covenant(s).

                        d.    Cross default to other debt.

                        e.    Bankruptcy, insolvency.

                        Other Events of Default as deemed appropriate in the
                        Agent's discretion.
<PAGE>   14

Party City Corporation
March 9, 1998
Page 14


Required Banks:         For the purpose of making amendments or waivers to the
                        credit agreement, approval by Banks whose commitments
                        under the Credit Facilities aggregate at least 66.67%
                        will be required. However, unless agreed to by all
                        Banks, no amendment or waiver shall change the principal
                        amount, reduce the rate of interest or fees, postpone
                        the scheduled payment of any principal, interest or
                        fees, release material collateral or change the
                        definition of Required Banks.

Assignments and
Participations:         Banks will be permitted to assign and participate their
                        portion of the Credit Facility. Assignments will be in
                        minimum amounts of $5,000,000 and assignees will be
                        subject to the consent of the Company and the Agent,
                        such consent not to be unreasonably withheld. In the
                        event of participation, as opposed to assignments,
                        voting rights to participants will be limited to change
                        in principal amount, reduction of the rate of interest
                        or fees, postponement of the scheduled payment of any
                        principal, interest or fees or release of any
                        collateral. Assignments will be subject to the payment
                        by the assigning Bank of a $3,500 service fee to the
                        Agent.

Governing Law:          This commitment shall be governed by and construed in
                        accordance with the laws of the State of New Jersey. The
                        parties will consent to New Jersey jurisdiction and will
                        waive all rights to jury trial.
<PAGE>   15

Party City Corporation
March 9, 1998
Page 15


                    PRICING GRID FOR PARTY CITY CORPORATION*

<TABLE>
<CAPTION>
===================================================================================================================================
                  LEVEL I               LEVEL II                  LEVEL III                LEVEL IV                 LEVEL V
-----------------------------------------------------------------------------------------------------------------------------------
Basis         The Company's        The Company's            The Company's            The Company's            The Company's
for           Fixed Charge         Fixed Charge             Fixed Charge             Fixed Charge             Fixed Charge
Pricing       Coverage Ratio is    Coverage Ratio is        Coverage Ratio is        Coverage Ratio is        Coverage Ratio is
              greater than 1.90:1  is less than or equal to is less than or equal to is less than or equal to is less than or equal
                                   1.90:1 but greater       1.70:1 but greater       to 1.50:1 and            to 1.35:1 and greater
                                   than 1.70:1              than 1.50:1              greater than 1.35:1      than 1.20:1
-----------------------------------------------------------------------------------------------------------------------------------
<S>                 <C>                   <C>                       <C>                     <C>                      <C>
LIBOR +               75                  100                       125                     150                      175
-----------------------------------------------------------------------------------------------------------------------------------
Base Rate +            0                    0                         0                       0                        0
-----------------------------------------------------------------------------------------------------------------------------------
Commitment Fee      17.5                   20                        25                      30                       35
===================================================================================================================================
</TABLE>

All prices are expressed in basis points.

*Initial Pricing shall be at Level III.