Ryan, Ash Ketchum, Simba, Alex, Alvin, Baby Kermit, Baby Bugs Bunny, Papa Smurf, Pooh, Bobby Brady, Cindy Brady, Oliver, Littlefoot, the characters and Kids World's Adventures Team meet Scott Calvin (Tim Allen) a divorced father and advertising executive with a young son, Charlie (Eric Lloyd). On Christmas Eve, Charlie comes over to spend the night with Scott before going back to his mother's for Christmas Day. That night, they are awakened by a clatter on the roof. Going outside to investigate, Scott can see someone on the roof. He yells at the trespasser, which causes the man to lose his balance and falls off the roof. The trespasser appears to be Santa Claus. He magically disappears, but his suit remains. They find a business card in a pocket stating that if something should happen to him, someone should put on the suit, and the reindeer will know what to do. They find a sleigh and eight reindeer perched atop the house. Scott puts on the Santa suit to please Charlie, and begins delivering toys from rooftop to rooftop. Their final stop is the North Pole. The head Elf, Bernard (David Krumholtz), shows him a tiny inscription on the card which says that, upon the death of the previous occupant, whoever wears the suit assumes the identity of Santa Claus and all the responsibilities that go with it. This is the "Santa Clause," as stated by Bernard: "You put on the suit, you're the big guy." He also gives Charlie a snow globe. Then, he meets an elf named Judy who tells Scott that he only has eleven months, until the next Thanksgiving to get his affairs in order before becoming Santa Claus full time, which he tries to refuse. Charlie and he spend the night at the factory. The next morning they awake back in Scott's home, where the only indication of their previous night's adventure is Scott's new silk pajamas with "SC" (Santa Claus or Scott Calvin) monogrammed on them. Scott dismisses it all as a dream. Soon, however, Scott starts gaining weight and his boss Mr. Whittle (Peter Boyle) likens him to the Pillsbury Doughboy. He develops a ravenous taste for Christmas treats, like Christmas cookies and hot cocoa. He grows a long white beard, and shaving it off has no effect; it regrows instantly. His hair whitens, despite all attempts to dye it. He somehow knows who has been "naughty" and "nice". Children (who somehow know he is Santa despite Scott not dressing like Santa) approach him with gift requests. Scott's rapid transformation worries his ex-wife Laura (Wendy Crewson) and her new husband, psychiatrist Dr. Neil Miller (Judge Reinhold), who try to terminate his visitation rights to Charlie. They question Scott's mental stability, and believe that Scott's changes are attempts at getting his son to like him. Eventually, Scott's visitation rights to Charlie are taken away. Disheartened, Scott begins to lose some of his certainty about his job as Santa. While visiting Charlie on Thanksgiving, Charlie's insistence that Scott is Santa reawakens Scott's magic and he, with Bernard's help, whisks Charlie away to the North Pole. Laura and Neil, who think Scott And The Gang have kidnapped Charlie against his will, call the police, who make a massive investigation. Meanwhile, at the North Pole, Charlie helps Scott and the elves perfect a new sled and communication devices. He calls occasionally, but this only reinforces Laura and Neil's belief that he is being held against his will. Eventually, Scott, as Santa Claus, goes on with his Christmas Eve trip, but is arrested while delivering presents to his son's home, and is accused of kidnapping Charlie. A team of rescue-elves, the ELFS, free Scott from jail by tying up the front desk guard, and fly Scott and Charlie home to his mother and stepfather, to whom Scott/Santa gives the presents they always wanted since childhood but never got: Laura gets a vintage Mystery Date game and Neil gets an Oscar Mayer "Wienie Whistle". (It was because of their not getting these presents that they became convinced Santa did not exist.) Laura, realizing finally that Scott really is the new Santa, tosses the custody papers into the fireplace and welcomes Scott to come to see Charlie any time that he wants. Bernard tells Charlie that the snow globe is magical. Anytime he wants his father to visit, all he has to do is shake it. After ten minutes, he shakes it and Scott comes back, says he was off to Cleveland, and takes Charlie with Ryan, Alvin, Baby Kermit, Baby Bugs Bunny, Papa Smurf, Pooh, Bobby Brady, Cindy Brady, Oliver, Littlefoot, the characters and Kids World's Adventures Team Have Become The Heroes That Save Christmas.
- Simba, Nala, Timon, Pumbaa, Zazu, Terk, Tantor, Louis, Genie, Sebastian, Baloo, King Louie, Fu Dog, Rutt and Tuke, Roger Rabbit, Sora, Donald Duck, Goofy, Ash Ketchum, Pikachu, Misty, Brock, Togepi, Stan Marsh, Kyle Broflovski, Eric Cartman, Kenny McCormick, Scooby-Doo, Shaggy Rogers, Fred Jones, Daphne Blake, Velma Dinkley, Mickey Mouse, Pluto, Taran, Princess Eilonwy, Fflewddur Fflam, Gurgi, Aladdin, Abu, Iago, Carpet, Jesse Greenwood, Elvis, Randolph Johnson, Nadine, The Goonies (Mikey Walsh, Brand Walsh, Mouth Devereaux, Data Wang, Chunk Cohen, Andy Carmichael, Stef Steinbrenner, and Sloth Fratelli), Jiminy Cricket, Kronk, Ttark, Woody Woodpecker, Jean-Bob, Speed, Puffin, Pterano, Fievel Mousekewitz, Tiger, Tony Toponi, Tanya Mousekewitz, Yasha Mousekewitz, Papa Mousekewitz, Mama Mousekewitz, Crysta, Batty Koda, Jack Skellington, Bugs Bunny, Daffy Duck, Aladar, Neera, Plio, Yar, Zini, Suri, Baylene, Eema, Url, Charlie Barkin, Itchy Itchiford, Chanticleer, Thomas the tank engine, Percy, James, Toby, Emily, Gordon, Henry, Edward, The Logging Locos (Bash, Dash and Ferdinand), Luke, Charlie, Hiro, Paxton, Victor, Kevin, Duck, Princess Twilight Sparkle, Applejack, Pinkie Pie, Fluttershy, Rainbow Dash, Rarity, Spike, The Cutie Mark Crusaders (Apple Bloom, Sweetie Belle and Scootaloo), Shining Armor, Princess Cadence, Heckle and Jeckle, Cool McCool, Princess Irene, Turnip and Curdie, SpongeBob SquarePants, Patrick Star, The Vultures (Buzzie, Flaps, Dizzy, and Ziggy), Toaster, Lampy, Radio, Blanky, Kirby, Rex, Woog, Elsa, Dweeb, Yogi Bear, Boo-Boo Bear, Snagglepuss, Huckleberry Hound, Quick Draw McGraw, Augie Doggie and Doggie Daddy, Wally Gator, Magilla Gorilla, Top Cat, Peter Potamus, Robin Hood, Little John, Devon and Cornwall, Mushu, SpongeBob SquarePants, Patrick Star, Squidward Tentacles, Sandy Cheeks, Eugene Krabs, Stan Marsh, Kyle Broflovski, Eric Cartman, Kenny McCormick, Mickey Mouse, Donald Duck, Goofy, Bugs Bunny, Daffy Duck, Simba, Nala, Timon, Pumbaa, Zazu, Alex, Marty, Melman, Gloria, King Julien, Maurice, Mort, The Penguins of Madagascar (Skipper, Kolwalski, Rico, and Private), Terk, Tantor, Louis, Ray the Firefly, Taran, Princess Eilonwy, Fflewddur Fflam, Gurgi, Orddu, Orgoch, and Orwen, The Flying Dutchman, Aladdin, Princess Jasmine, Abu, Iago, Genie, Sebastian, Jesse, Elvis, Randolph Johnson, Nadine, Celebi, The Goonies (Mikey Walsh, Brand Walsh, Mouth Devereaux, Data Wang, Chunk Cohen, Andy Carmichael, Stef Steinbrenner, and Sloth Fratelli), Rex, Woog, Elsa, Dweeb, Kenai, Koda, Rutt and Tuke, Baloo, Bagheera, King Louie, The Vultures (Buzzie, Flaps, Dizzy, and Ziggy), Jiminy Cricket, Kronk, Fu Dog, Roger Rabbit, Aladar, Neera, Plio, Yar, Zini, Suri, Baylene, Eema, Url, Scooby-Doo, Shaggy Rogers, Fred Jones, Daphne Blake, Velma Dinkley, Barney the Dinosaur and the gang, Baby Bop, BJ, Riff, Jake Sully, Neytiri, Crysta, Batty Koda, Chanticleer, Charlie, Itchy, Jack Skellington, Kids World's Adventures Team, and the characters will guest star in this movie.