It's December 1910, and Mrs. Santa Claus (Angela Lansbury) is having marital woes. Her husband Nicholas (Charles Durning) is so invested in his work, he pays her no attention. She has an idea for a new route he should try during his annual toy delivery, but when she can't convince him to even give her a hearing, she takes the sleigh and one of the reindeer to go try it out for herself, with only the head elf Arvo knowing where she's gone. When she gets blown off course, she ends up on the Lower East Side of Manhattan and finds herself stranded there for the time being.
Determined to make the most of it, Mrs. Claus (using the name "Mrs. North") rents a room from a widowed Jewish woman, Mrs. Lowenstein, and gets involved in minor subplots regarding her neighbors. Mrs. Lowenstein left her home country due to civil unrest, and cannot let herself fully unpack in her new home in case she has to escape in a hurry again. Her daughter Sadie is a crusader for women's rights, much to the distress of her mother, who is convinced that she's going to get arrested. Sadie is the object of the affections of a fellow immigrant, Marcello, who is pretty much the only person who will even listen to her street preaching. Another neighbor is young Nora, who keeps skipping school to work so she can help her father pay for her mother and baby brother to come to America from Ireland. She's the one who helps "Mrs. North" get a job at Tavish Toys, where the owner deliberately makes toys guaranteed to fall apart on the children who play with them. Meanwhile, back in the North Pole, Arvo is starting to panic because not only is Santa growing depressed, but since Mrs. Claus took the sleigh, Christmas itself is endangered.
Tropes Mrs. Claus took with her in the sleigh:
- Affectionate Nickname: Mrs. Claus calls her husband "Nicky."
- All of the Other Reindeer: Literally. Mrs. North speaks the name of each reindeer in the same succession as they're listed in a certain song.
- Artistic License History: In 1910, there were only 46 United States; New Mexico and Arizona didn't become states until two years later. However, the American flag used in one scene has 48 stars.
- The Coconut Effect: A street Santa collecting money for charity wears a red suit, something that wouldn't figure into the public image of Santa Claus until Coca-Cola used it in one of their ads in 1930. But the red suit is so ingrained in our concept of the character that they had to use one or it wouldn't be obvious who the man was supposed to be.
- Creator Cameo: Jerry Herman appears in the Massive Multiplayer Ensemble Number as Mrs. North learns about the world of Avenue A.
- A Day in Her Apron: Not Santa, but Arvo, who in Mrs. Claus's absence has to do several of her usual tasks. Among these is making cocoa for the jolly guy, who finally realizes something is very wrong when he tastes the cocoa.
- Everyone Is Christian at Christmas: Mrs. Lowenstein gives Mrs. North a brief lesson of Hanukkah, but mentions that she enjoys Christmas more than she should.
- Happily Married: The Clauses really love each other and they are this most of the time; it's just that Nicholas gets so very distracted about Christmas.
- Happy Ending: For everyone. Mrs. Lowenstein finally starts to relax in her home rather than constantly being prepared to flee again, and receives a candlestick to match the one she brought with her from the old country. Sadie and Marcello are in the beginning of a sweet romance, and Sadie's soapboxing has helped some of the other immigrant women understand that their views are important. Tavish has seen the error of his ways. Nora's mother and brother arrive at the apartment just in time for Christmas. And Mrs. Claus has been reunited with her apologetic husband, who gives her beautiful Christmas gifts and takes her on his toy delivery run with him - using the route she devised.
- "I Am" Song: "I'm Mrs. Santa Claus; yes, I'm married to him..."
- I Have Your Wife: And your reindeer. Tavish does this briefly, right before his HeelFace Turn.
- Just Whistle: Mrs. North and Nora sing a song to defer their nervousness regarding the impending work action.
- Last-Name Basis: We never do find out what Mrs. Claus's first name is. The only person who might use it, Nicholas, usually calls her "dear."
- Married to the Job: Nicholas/Santa being this is what kicks off the plot.
- Meaningful Rename: Mrs. Claus realizes, upon introducing herself, that she can't use her real name. She says instead that she's "from the north" and decides to adopt the name "Mrs. North" while she's in New York. Later, Augustus reveals that he's figured out Mrs. North's true identity.
- Missing Mom: Nora's isn't dead, just absent. The family didn't have enough money for them all to immigrate at once, so Nora and her father came to America and are trying to earn enough to buy ship's passage for her mother and infant brother.
- Musical Theatre: And made for television at that!
- My God, What Have I Done?: This is Santa's basic reaction to being told that his wife has been gone for two entire days and he didn't even notice.
- Opposites Attract: Sadie and Marcello sing about how much they don't go together (at all) until they realize this.
- Singing Voice Dissonance: When Sadie and Marcello are getting close to their First Kiss, she belts out in his face.
- Single-Issue Psychology: Mrs. Claus figures out why Augustus Tavish has such an issue with toys in general and Christmas in particular: when he was a boy, Santa brought him the toy he really wanted, only to have it almost immediately destroyed by his little stepbrother, and from that time on he refused to ask Santa for anything. It's unclear why he blamed Santa for the incident, but he's genuinely shocked to hear that Santa noticed he stopped writing.
- Soapbox Sadie: Sadie is literally this - her introductory scene shows her standing on a soapbox, lecturing passersby about suffrage, and her name is Sadie!
- Villain Song: In spades. Not only does Tavish get his own hammy toy-making song, it is an eerie echo of Mrs. Claus's opening song, bordering on a Dark Reprise.
- Widow Woman: Mrs. Lowenstein