|Weekenders Visits Halloweentown|
The film begins with 13-year-old Marnie Piper (Kimberly J. Brown) and her mother, Gwen (Judith Hoag), arguing over why she and her younger siblings 12-year-old Dylan (Joey Zimmerman) and 7-year-old Sophie (Emily Roeske) can never go out for Halloween, and why Marnie cannot go to a costume party. Her mom offers no clear explanation. Gwen's mother Aggie (Debbie Reynolds), who is an expert witch, shows up for her annual Halloweenvisit. The children are happier to see Aggie than Gwen is, as Aggie openly encourages the children to get more involved in Halloween.
Unknown to Marnie, Aggie is intent on training Marnie as a witch. Before heading home, Aggie reads the children a bedtime story called "Halloweentown", a mystical place where witches, vampires and monsters of all sorts live in peace. Sophie points out a drawing of a witch in the book that resembles Marnie; Aggie does nothing to stop Marnie from imagining such a thing. Gwen and Aggie then get into an argument. Gwen insists Marnie will be raised as a normal person and not a witch. Aggie says she disagrees, but actually she is there for another reason: people have suddenly started mysteriously disappearing in her hometown. Gwen thinks they just moved, but Aggie says it is not that simple. Aggie desperately asks for Gwen's help, but Gwen declines. Marnie overhears the argument.
When Aggie leaves to return home, Marnie and Dylan follow her. They see Aggie getting onto a magical bus, and sneak onto it through the back door. When they arrive in Halloweentown, Aggie does not see Marnie and Dylan getting off the bus, and the children lose sight of her. At the same time, Marnie and Dylan realize Sophie snuck onto the bus. They begin looking for Aggie, and are approached by Kalabar (Robin Thomas), the Mayor of Halloweentown. He whistles for a cab which is driven by Benny (voice of Rino Romano), a skeleton with a bad sense of humor. The children find their grandmother's home, and against her better judgment, Aggie decides not to take them home immediately. She says she will start Marnie's witch training, but has to take care of "the bad thing" first. She shows her grandchildren what she is talking about: in her cauldron, a vision of a hooded demon appears, laughing maniacally. She says she must activate Merlin's talisman with a spell and potion to defeat the demon.
In town, the family is introduced to Luke (Phillip Van Dyke), a goblin who was made handsome by a shadow demon. He makes a clumsy pass at Marnie, which she turns down on the spot. Gwen arrives in Halloweentown with plans to bring her children home, much to Marnie's objections. Gwen cannot find another bus back to the mortal world and decides to see if the mayor can do anything to help. She is shocked to see that the mayor is Kalabar, an ex-boyfriend of hers. When Kalabar briefly leaves to handle another problem, Gwen and her children see Aggie walking somewhere with Luke. Sensing Aggie might be in trouble, they follow Aggie and Luke to an abandoned movie theater.
Aggie meets the hooded demon in the theater, where Halloweentown citizens have been frozen in time. Aggie declines to give the talisman to the demon. Gwen and the children enter the theater as Luke rushes out in fear. The demon freezes Gwen and Aggie. The children escape, and obtain the necessary ingredients–the hair of a werewolf, the sweat of a ghost, and a vampire's fang–to make the talisman regain its power. They then realize they must install the talisman in the large jack- o'-lantern in the center of the town.
When they arrive to install it, the demon suddenly appears and reveals himself to be Kalabar. He starts talking to the townspeople and tries to persuade them to join him and take over the mortal world. With the help of Luke, Marnie slips past Kalabar long enough to climb up onto the jack-o'-lantern and try to place the talisman inside. Kalabar, noticing her, freezes her. As she is about to pass out, Marnie drops the talisman inside the jack-o'-lantern, lighting it and unfreezing herself and everyone trapped inside the theater. Gwen, Aggie, and the children confront Kalabar and use their powers to defeat him. The film ends with the family getting on the bus and blasting off to the mortal world.
- Ash Ketchum, Pikachu, Misty, Togepi, Brock, Littlefoot, Cera, Ducky, Petrie, Spike, Serena and the Sailor Scouts, Scooby-Doo, Shaggy Rogers, Fred Jones, Daphne Blake, Velma Dinkley, Kazuto Izuka, Narue Nanase, Masaki Maruo, Hajime Yagi, Kanaka Nanase, Olivia, Stephanie, Emma, Mia, Andrea, Kurumi Tokisaki, The Dazzlings, The Crime Empire (Joker, Harley Quinn, Penguin, Two-Face, Negaduck, Quackerjack, Megavolt, Bushroot, and The Liquidator), Megan, Kyoko Kudo, Yuki Kashiwazaki, Aya Kanazawa, The Grand Duke of Owls, and Team Rocket (Attila and Hun, Jessie, James, and Meowth) will guest stars in this film.
- Kurumi Tokisaki, The Dazzlings, The Crime Empire, Megan, Kyoko Kudo, Yuki Kashiwazaki, Aya Kanazawa, The Grand Duke of Owls, and Team Rocket will work for Kalabar.
- This film will be dedicated in memory of Debbie Reynolds, considering her death from intracerebral hemorrhage in 2016.
- The storyline continues in Weekenders Visits Halloweentown II: Kalabar's Revenge.