The scene where Polly tapes up the jack in the box containing Fred was based off an actual incident that happened to a friend of co-writer/executive producer Carlos Davis named Steve Burnette. Burnette's mother Gloria had an imaginary friend when she was a little girl. But the girl's mother couldn't stand the fact that her daughter had an imaginary friend. It finally got to the point to where the Gloria's mother took her imaginary friend and flushed it down the toilet. This incident traumatized her for three years.
Robin Williams was offered the role of Drop Dead Fred, but instead chose to play Peter Banning in Hook (1991). Rik Mayall played Drop Dead Fred instead. Mayall and Williams both died in the summer of 2014.
Grandma Bunce is played by the director's mother. For the scene where she gets paint thrown on her, yogurt was used. Weeks later, she said she still found some yogurt in her ears.
Paul Webster, Anthony Fingleton: Both producer and co-writer/co-executive producer uncredited appearances in the film. Webster is the guy who breaks into Lizzie's car and steals her purse, and Fingleton is one of the wine tasters at Charles' wine tasting party.