Joe Pesci deliberately avoided Macaulay Culkin on-set because he wanted Culkin to think he was mean.
The picture Kevin finds of Buzz's girlfriend was a picture of a boy made up to look like a girl, because director Chris Columbus thought it would be too cruel to make fun of a girl like that. The boy that was used in the photo was art director Dan Webster's son.
Joe Pesci was used to adding profanity to most of his scripts, and kept forgetting that he was filming a family movie during his character's on-screen outbursts, so director Chris Columbus advised him to say "fridge" instead of the "f" word. A lot of Pesci's unintelligible pained mutterings were his way to avoid cursing.
John Candy shared all of his screentime with Catherine O'Hara. The two previously worked together on SCTV (1976), and were good friends. Candy died on O'Hara's 40th birthday, and O'Hara gave a tearful eulogy at his funeral.
Raja Gosnell: This movie's editor is the voice on the answering machine when Harry and Marv are robbing their first house. He later made his directorial debut with Home Alone 3 (1997).