From Mental Floss.
IT'S A WONDERFUL LIFE
The gym floor that opens up to reveal a swimming pool was real and was located at Beverly Hills High School in Los Angeles.
The movie received the “honor” of getting its own FBI file in 1947, when an analyst submitted the idea that the film was an obvious attempt to discredit bankers, a “common trick used by Communists.”
Among other people, the notoriously cynical Dorothy Parker contributed some rewrites to the script.
Vincent Price was considered for the part of Mr. Potter.
During the scene where Carol Kane grabs Bill Murray’s lip, she really latched on and accidentally tore it so badly that they had to stop filming for a few days so Bill could heal.
All three of Bill Murray’s actor brothers--Brian Doyle-Murray, Joel Murray and John Murray--appear in the movie.
That’s Paul Shaffer leading the street carolers Bill Murray insults. The other carolers are Miles Davis (yep, that Miles Davis), famous saxophone player David Sanborn and Grammy-winning jazz guitarist Larry Carlton.
A CHRISTMAS STORY
Ralphie says he wants the Red Ryder BB Gun 28 times throughout the course of the movie.
Jack Nicholson wanted to play Ralphie’s dad in the film but the film's budget couldn't afford him.
An episode of the TV show Mythbusters proved that it is possible to get your tongue stuck on a piece of cold metal.
NATIONAL LAMPOON'S CHRISTMAS VACATION
The scene where the cat bites on the Christmas lights cord and gets electrocuted was nearly cut from the movie. Studio execs wanted the scene taken out until test screening audiences scored it as their favorite moment in the entire movie.
After Clark Griswold (Chevy Chase) unsuccessfully attempts to demonstrate his handiwork with the house Christmas lights to his family, he asks his son, Rusty (Johnny Galecki), to help him check all the light bulbs again. Rusty looks at his bare wrist, pretending to have a watch, and excuses himself. Looking at a bare wrist and pretending to have a watch is one of Chevy Chase's trademark gags.
The idea for the film originated in 1993, and Jim Carrey was reportedly slated to play the lead.
Gimbels Department Store was a real store and competitor of Macy’s until it closed in 1987.
Ming Ming the elf from the beginning of the movie is Peter Billingsley, the actor who played Ralphie in A Christmas Story.
MIRACLE ON 34th STREET
The scenes of the Macy’s Thanksgiving Day Parade are actually taken from the 1946 parade. The movie is credited with bringing the traditional parade to the national spotlight, and Macy’s employees were given half a day off so they could see the first showing of the movie. In fact…
Edmund Gwenn, who played Santa Claus, was also Santa Claus during the real 1946 Macy’s Thanksgiving Day Parade.
Macaulay Culkin still has physical evidence of Kevin McAllister – in the scene where Harry bites Kevin’s finger, Joe Pesci bit harder than he’d intended and left Mac with a scar.
Daniel Stern wasn’t crazy about having to film a scene with a tarantula on his face, but agreed to it in the condition that they do just one take. His scream had to be dubbed in later because a real scream would have scared the tarantula.
THE BELLS OF ST. MARY'S
The production was overseen by a Catholic priest who served as an advisor during the shooting. While the final farewell sequence was being filmed, Bing Crosby and Ingrid Bergman decided to play a prank on him. They asked director Leo McCarey to allow one more take, and, as "Father O'Malley" and "Sister Benedict" said their last goodbyes, they embraced in a passionate kiss, while the offscreen priest-advisor jumped up roaring in protest.
The movie was the first sequel (Going My Way) to be nominated for a Best Picture Oscar.
Full list here.