The character of Hal Weidmann is based on Hal Ashby.
Robert Downey Jr. was originally slated to play Eddie. John Cusack was cast instead when Downey's legal problems raised doubts as to whether he would be available for filming.
'Roberts, Julia' turned down the lead role for the supporting one.
This was Joe Roth's first picture as director in 11 years. Initially Billy Crystal was slated to direct the picture. When Roth read the script, he was totally immersed and liked the script so much that he wanted to direct. Crystal granted Roth's request to direct the picture and stayed on as producer.
When Hal is talking to the press at the press junket his microphone shorts. As he says the line "...this is the most honest movie I have ever made" after the word "made" you hear a click and can see the flash in the microphone headpiece as it shorts.
Gwen uses "Holly Golightly" as an alias for the hotel register, something Catherine Zeta-Jones has wanted to do for real for years.
Billy Crystal had written the part of Eddie for himself years ago, but director Joe Roth persuaded Crystal to take on the role of Lee the publicist, as he felt Crystal was too old to play the part by then.