Robert Downey Jr.'s character, David Barnes, was originally written as a 50 year old man. But director Michael Hoffman, who had worked with Downey before on an unfinished film called "Back East", suggested the part was rewritten to fit Downey's age.
A poster in Kevin Kline's dressing room lists him as playing "Willie Loman." The name should be spelled "Willy." The production wasn't that polished to begin with, so it wouldn't be surprising if no one proofread the poster.
When Celeste goes to Jeffrey's apartment to "rescue" Laurie, she tricks the doorman into telling her that Jeffrey's apartment is 2D. When she leaves, his door clearly says 2A.