Although Carl Bentley is shown to have still been an adult when Allen Parrish was a child, David Alan Grier, who plays Carl, is actually four years younger than Robin Williams, who plays the adult Allen. Williams was also ten years older than Bonnie Hunt, although they play characters who were children together.
When Van Pelt enters the gun store, the music playing on the radio has been modified for the Mexican release due to the fact that, at least in the U.S. release, it originally featured Mexico's national anthem. It is an infringement of Mexican law to play the anthem for commercial or mockery situations, deliberately or not, although in the U.S. Territories it is in the public domain.
During a guest appearance on Clive Anderson All Talk (1996), a UK chat show, Robin Williams told a story about filming the scene where Alan wrestles a crocodile. He said that in one take he got a little carried away and thumped the crocodile with his elbow, forgetting that there was a man inside the suit. He heard a voice inside the crocodile yell "Hey!" in protest.
When asked in a roundtable interview whether Parrish's father was like Robin Williams' own, the actor admitted a slight comparison. "He was a bit stern and kind of elegant," Williams said. However, the actor likened the disconnected relationship between Alan and his father to the fractured relationship between his dad and grandfather. "The wonderful thing about [my dad] is he would never force me to do anything ... because something had happened early in his life where he didn't want that to happen to me. He had to give up a dream," Williams continued. "His father had been very wealthy and when his father died, they lost all of that and he was forced to work at a strip mine in Pennsylvania ... When I found something I loved, [my dad] saw that ... That's what makes it nice, when you can connect on that level."
The gun shop owner asking Van Pelt if he's a postal worker. Around the time of the movie, there had been a lot of news stories about postal workers going crazy and shooting up their workplaces, from which we get the expression "Going Postal."
In the Christmas party scene at the end, "Hark the Herald Angels Sing" is being being played on the piano and sung by the guests; this is an homage to the closing scene in It's a Wonderful Life; which has a similar theme of an imaginary alternate reality that returns to reality at the end of the movie.
The music heard on the radio while Van Pelt is in the gun shop (the Mexican national anthem in the U.S. release) is from a Berliner Gramophone disc record performed by Sousa's Band, recorded April 7, 1898.
The Sir-Save-A-Lot sequence was shot at 56th Street & 12th Avenue, Tsawwassen, BC, in what had been the Tsawwassen Shoppers Mall. The store had been a Super Valu grocery store before it closed. At the time of filming, the store was vacant, and although the exterior was repaired after the movie was shot, the store never re-opened. The mall has since been redeveloped, with Safeway being the anchor tenant. The Sir-Save-A-Lot/Super Valu in the old mall was along the west perimeter of the current mall, what is now a parking lot/entranceway.
The trivia items below may give away important plot points.
Though the movie's plot differs greatly from that of the book on which it is based, the ending of the film is very similar, in which the game is found by two other young children. In the book, the two children who find the game at the end are named Walter and Danny, the main characters from Zathura: A Space Adventure (2005).
In the French version (at least as dubbed in Quebec), Judy's line, "I'm sorry, dear, you have the wrong number," which she speaks in a fake British accent, is still in English, but spoken in a North American accent. Additionally, the two French girls who hear the game at the very end speak Spanish instead of French.
In the version of reality where the game is unfinished, Samuel Alan Parrish was born on June 18, 1921 and died on May 6, 1991. Carol Anne Parrish was born on November 20, 1930 and died on August 19, 1991. They are still alive in the post-game version.
It was actually a crocodile -- as opposed to an alligator -- that Alan wrestled for Sarah during the monsoon that floods the house. Alan points out the difference to Sarah afterwards, explaining that alligators don't have that "fringe".