The three kids who run between Jimmy and Oz when they are standing next to the flower cart are Bruce Willis's three daughters, Tallulah Willis, Scout Willis, and Rumer Willis.
The blues song that plays as Oz arrives in Chicago and meets his friend at the Oyster Bar is performed by Bruce Willis and his band. The harmonica solo featured in the song is played by Willis himself.
The shot of Jill (Amanda Peet) twisting her ankle was not scripted. Director Jonathan Lynn liked the take, so it was put into the film.
The house used for filming was infested with flies, so it was nearly impossible to prevent them from appearing in several scenes.
The owners of the two houses that were used for this movie were paid $50,000 on the condition that they left their houses for a month.