Conversation so far:
What were some of Cosmo Kramer's pseudonyms?
He used the name H.E. Pennypacker
Which episode did Cosmo Kramer use this name in?
in The Puerto Rican Day“
What happened in the Seinfeld episode The Puerto Rican Day?
Kramer poses as a prospective buyer interested in an elegant apartment in order to use its bathroom
What other names does Cosmo Kramer use?
He also uses Dr. Martin van Nostrand
Which episode does Cosmo Kramer use this name in?
In the episode The Package

Question: What is the main plot of that episode?
Self-contained rewrite: What is the main plot of The Package?