Meet Me in St. Louis (1944)

Continuity mistake: The levels of soup in people's bowls change during the dinner scene at the beginning.

Agnes Smith: Katie, where's my cat?
Katie the Maid: I don't know... a little while ago, she got in my way and I kicked her down the cellar steps. I could hear her spine hitting on every step.
Agnes Smith: Oh, if you killed her, I'll kill you! I'll stab you to death in your sleep, then I'll tie your body to two wild horses until you're pulled apart.
Katie the Maid: Oh, won't that be terrible, now? There's your cat.

Trivia: In the film, when Margaret O'Brien is sad because she doesn't want to move, she knocks down snowmen and cries hysterically. It is rumored that in real life Margaret was told that her dog died when it really hadn't, just so she would cry. Apparently Margaret O'Brien denies this, claiming this story is not true. She explains that though she didn't feel it was easy to cry, she was able to muster it after being told that June Allyson - her MGM rival in sobbing - could cry on cue.

Question: What is the name of the last song they dance to at the Christmas dance? I know I've heard it before, but I can't put a name on it.

Jennifer 1