It's December 1910, and Mrs. 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 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 while Cupid the Reindeer recovers from a sprained ankle.
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 works 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 Musicals Are Adaptations: Averted! The musical is not an adaptation of any preexisting story, unless you count the Santa mythos in general.
- 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.
- Anti-Love Song: "We Don't Go Together at All" starts off as one, but naturally does not end as one.
- 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.
- Blithe Spirit: On Avenue A, Mrs. Claus improves the lives of everyone she meets, even Mr. Tavish in the end. Not knowing that she's the genuine article, Sadie declares that she's been "the Mrs. Santa Claus of Avenue A."
- Child Hater: Mr. Tavish, according to his Villain Song anyway:Of Yuletide smiles I'm always cautious
'Cause those dimpled faces make me nauseous
So, to each sweet girl and boy
You deserve a Tavish toy - 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.
- Crowd Song: "Avenue A" is sung by everyone on the eponymous Manhattan street. "Suffragette March" is another example.
- Dark Reprise: "A Tavish Toy" is a dark inverted version of "Seven Days 'Til Christmas"
- 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 that something is very wrong when he tastes the cocoa.
- The Edwardian Era: Set in 1910. According to IMDb trivia, the time period was chosen on the basis that the costumes of that era would flatter Angela Lansbury. Apparently, it was previously suggested that the film should take place in The Roaring '20s, but they didn't think the flapper look would work for her.
- Everyone Is Christian at Christmas: Mrs. Lowenstein gives Mrs. North a brief lesson on Hanukkah, but mentions that she enjoys Christmas more than she should.
- Evil Is Hammy: Terrence Mann is having a lot of fun playing Mr. Tavish.
- Final Love Duet: "The Best Christmas of All," sung by Mr. and Mrs. Santa Claus.
- 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.
- High Turnover Rate: Mr. Tavish's supervisor, apparently. Mrs. North doesn't last very long in the position either.
- "I Am" Song: The title character has two: "Mrs. Santa Claus" (which doubles as an "I Want" Song) and "Almost Young."
- I Have Your Wife: And your reindeer. Tavish does this briefly, right before his Heel–Face Turn.
- Just Whistle: Mrs. North and Nora sing a song to defer their nervousness regarding the impending work action.
- Last-Name Basis: Averted. Santa a couple of times calls her by her first name: Anna.
- Little Girls Kick Shins: Nora does this to Officer Doyle in her first scene, establishing her as an incorrigible brat. She gets better.
- 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, Tavish 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.
- Officer O'Hara: Officer Doyle, the film's token police officer, is very Irish. Very appropriate for New York in 1910.
- Opposites Attract: Sadie and Marcello sing about how much they don't go together (at all) until they realize this.
- Really 700 Years Old: The Clauses, of course. In her titular "I Want" Song, Mrs. Santa Claus indicates that she has been around "for centuries." In "Almost Young," she says, in what may be a Sarcastic Confession, that she's a million years old.
- 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!
- The Suffragette: Sadie and, eventually, a whole army of women from Avenue A. They get the song "Suffragette March."
- Triumphant Reprise: "Suffragette March" is a triumphant version of "Mrs. Santa Claus", the longing "I Want" Song from the beginning of the movie.
- Unlimited Wardrobe: Despite having no money, Mrs. North is able to acquire a seemingly endless supply of fancy Edwardian dresses. There's a throwaway line explaining that she bought it all secondhand on credit. Sure. We can only assume that her creditors were left fuming when she disappeared on Christmas Eve. Either that or Tavish paid her a lot more than his cheapskate ways would suggest.
- Uptight Loves Wild: Sadie is straitlaced while Marcello is much more easygoing. Ironic, considering Sadie is the one with the radical (for the time) politics.
- 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, as noted under Dark Reprise.
