Michael Palin's father stuttered, so Palin used a lot of his real-life experience when playing Ken Pile, including the fact that Ken's stutter is less pronounced around people he trusts (George Thomason and Wanda Gershwitz) and worse around people with whom he is uncomfortable (Otto West).
Jamie Lee Curtis buried her face in pillows during Kevin Kline's ejaculation scene, to keep her from bursting out laughing at the faces he was making.
Actor, executive producer, and writer John Cleese chose the name "Archie Leach", Cary Grant's real name, because he was born twenty miles away from where Grant was born (Hughenden Road, Horfield, Bristol, England), and because it was the closest Cleese could get to being Grant.
The fish that Kevin Kline ate were made out of Jell-O. Kline claims that he offered to eat live fish, but the filmmakers wouldn't let him.