Lionel Barrymore was originally to play Ebeneezer Scrooge in the movie version of A Christmas Carol, but suffered an injury. He played the role on radio every year. Because he was so good at playing Scrooge, Frank Capra chose him to play Old Man Potter in It's a Wonderful Life.
In this scene from Santa Claus Conquers The Martians, the kids defeat the bad guy, Voldar, using toys (provided by Ideal Toys). MST3K and others have pointed out the violent and dangerous nature of some of the toys used. The film was made in 1964. A year after that film came out a movement by parents to have toy company stop selling war oriented toys. It was around this time that New York radio personality talked to a "concerned woman" in a coffee shop about the "Ban War Toys" movement. It brought back a memory from his childhood of wanting a Red Ryder BB gun and being to by several adults "You'll shoot your eye out." That story was included in his book, In God We Trust, All Others Pay Cash. It became the basis for the movie A Christmas Story.
A Christmas Story was directed by Bob Clark, who also directed a horror film called Black Christmas in 1974 (Above). Peter Billingsley, who played Ralphie in A Christmas Story, plays an elf named Ming-Ming in Elf.
Obviously, Holiday Inn and White Christmas have both Bing Crosby and "White Christmas" in common, but what does White Christmas and It's a Wonderful Life have in common? If you said Alfalfa, you're right. Former Our Gang/Little Rascals star Carl "Alfalfa" Switzer played Mary's date at the dance in It's a Wonderful Life (His big moment is opening the gym floor to plunge George and Mary into the swimming pool in an act of jealousy). In White Christmas, his in only shown in a photo (below) as Vera-Ellen's brother "Freckle Face" Benny Haynes.
Also the gag involving the photo is similar to the one in another Christmas film, Home Alone. Kevin finds a photo of his bully, big brother Butch's girlfriend (above), which cause Kevin to say, "WOOF!" (below) It is actually a photo of a boy in drag. Director John Hughes felt that using a photo of a "real girl" would be cruel.
The 1934 film version of Victor Herbert's Babes In Toyland, starring Laurel and Hardy, there are several joking references to Walt Disney, including a Mickey Mouse clone (Below) and Three Little Pigs (accompanied by "Who's Afraid of the Big Bad Wolf?" in the background).
Character actor Dick Elliot plays the Judge in Christmas in Connecticut. In It's a Wonderful Life, he is the neighbor, who yells at George Bailey, "WHY DON'T YA KISS HER?" when he is escorting Mary home.