BirthdayExpress Dr Seuss Party Supplies - Thank-You Notes (8) Includes (8) birthday party thank-you notes with envelopes. Add matching tableware, favors, accessories, or a party kit bundle to complete your Dr. Seuss birthday party. Features classic Dr. Seuss characters such as Cat in the Hat, Grinch, Horton, Sam I Am, Lorax, Thing 1, and Thing 2.