The Leg Lamp became a real product in 2003 when a fan of the film started manufacturing real lamps for sale. This then led to....
...the fan using the money he made from his business to buy the house in Cleveland that was used for exterior shots of Ralphie's house. He later dropped another quarter-million dollars to gut the house and remodel it to look like the sets that were used for interior scenes. The house across the street has been turned into a museum and Leg Lamp giftshop.
The specific BB Gun Ralphie wanted didn't exist; Jean Shephard had conflated several different models in his mind when he was writing the story. It exists now, though....
Miss Shields visiting Ralphie's parents at home to tell them how wonderful he is.
Ralphie saving Flash Gordon from Ming the Merciless on the planet Mongo.
Ralphie saving Santa Claus from Black Bart.
Enforced Method Acting: Apparently no one told Melinda Dillon that the waiters in the Chinese restaurant were going to bring in a cooked duck with the head still attached. Or chop its head off moments later. Her reactions to both of those occurrences are genuine.
Marathon Running: Every year, TBS runs the movie for twenty-four hours solid, beginning at 8 p.m. on Christmas Eve.
The Red Stapler: You can now buy a leg lamp. The Red Ryder BB gun is an aversion, however; while now available, they were produced throughout the 30-odd-year gap between the end of the Red Ryder Franchise and this film's appearance.
Not the particular model described in the film, however. note The Buck Jones air rifle has the compass and sundial in the stock, but none of the features of the Red Ryder. A special model was made for the movie to match Jean Shepherd's description in the story. While it may be Artistic License, it is the configuration Shepherd claims to remember.
Sequel Gap: The original came out in 1983. It took em 28 years to do a continuation.
Vindicated by Cable: Only moderately successful at the box office when originally released, the film achieved Cult Classic status in the late '80s thanks to TV and home video.
What Could Have Been: Jack Nicholson was apparently a fan of the short-stories, and really wanted to play Ralphie's Old Man (he was even willing to take a paycut if necessary!note This is the same guy whose salary consumed the bulk of the budget for Batman.). However, Jean Shepherd feared that the presence of such a high-profile actor in a supporting role would distract people from the main story.
In hindsight, it's hard to see anyone other than Darren McGavin in that role.
It would also be hard to see Nicholson swearing at the furnace being dubbed over by gibberish.