Billy Crystal had written the part of Eddie for himself years ago, but 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.
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.
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.
When Dave enters the hotel bar to speak with Lee, Dave says to the bartender "I'll have whatever he's having." This is an in-joke in reference to the famous "I'll have what she's having" scene in When Harry Met Sally... (1989), which also starred Billy Crystal.