During production, Richard Donner was shocked when Mel Gibson confided that he was drinking five pints of beer for breakfast. Despite his alcohol problems, Gibson was known for his professionalism and punctuality.
The scene where Mel Gibson attaches cables to the stilts of a mountain-top house and pulls it down cost over $500,000.
Jack McGee ad-libbed his line about the condom commercial during rehearsals. The cast and crew liked it so much, it was kept in the film.
Leo's "okay-okay-okay" schtick was based on Disneyland employees giving directions to guests at Fantasyland. Originally, Leo was going to be an oily, effeminate character, but Joe Pesci didn't want to play him that way. He pitched the idea of making Leo all-too-eager to please, complete with "okay-okay-okay" ad libs, to Richard Donner. Donner laughed and said, "Do that! Do that!" The phrase is referred to in Kevin - Allein zu Haus (1990) by having the phrase "Oh, K Plumbing" painted on a van driven by Joe Pesci's character.
Despite the film's anti-South African stance, it was passed uncut by the South African censors, and became a major financial success in that country.