When a boy's beloved dog passes away suddenly, he attempts to bring the animal back to life through a powerful science experiment.
When a car hits young Victor's pet dog Sparky, Victor decides to bring him back to life the only way he knows how. But when the bolt-necked "monster" wreaks havoc and terror in the hearts of Victor's neighbors, he has to convince them that Sparky's still the good, loyal friend he was.—Kathy Li
Young filmmaker and scientist Victor Frankenstein (Charlie Tahan) lives with his parents, Ben (Martin Short) and Susan Frankenstein (Catherine O'Hara) and dog Sparky in the quiet town of New Holland. Victor creates home-made short movies with normal household items, starring himself and his faithful canine friend Sparky, which displays his active imagination. Victor has the ability to fix projectors and other complex electrical and mechanical instruments. Ben and Susan are worried that Victor doesn't have any friends other than Sparky and spend all of his time in the attic.Ben is a travel agent.
Mayor Bergermeister is Victor's next-door neighbor and the town Mayor, who dislikes Sparky for always sniffing around in his immaculate garden. Elsa is Bergermeister's niece. Mayor Bergermeister is about to launch Dutch Day, which he considers a big occasion for the city.
Victor's intelligence is recognized by his classmates at school, his somber next-door neighbor, Elsa Van Helsing (Winona Ryder), mischievous, Igor-like Edgar "E", Gore (Atticus Shaffer), obese and gullible Bob (Robert Capron), overconfident Toshiaki (James Hiroyuki Liao), creepy Nassor (Martin Short) who thinks storms are caused by the windmills stirring up the air, and an eccentric girl nicknamed Weird Girl (Catherine O'Hara), but communicates little with them due to his relationship with his dog.
Mr. Rzykruski is the class's new science teacher, as their old science teacher was hit by lightning. New Holland was built on an abandoned Gold Mine and a Cemetery and has thunderstorms every night. Hence lightning strikes are very frequent. Nassor believes that the windmills of New Holland churn the sky, making it angry and hence it strikes in the form of lightning.Mr. Rzykruski asks the class to prepare for the science fair, announcing a substantial prize for the winner.
Weird girl has a cat named Mr Whiskers, who has a quality that when she dreams about someone, she makes a poo like the first letter of their name & then something big (good or bad) happens to them. This time Whiskers has dreamed about Victor.
Concerned with his son's isolation, Victor's father encourages him to take up baseball and make achievements outside of science. Victor hits a home run at his first game, but Sparky, pursuing the ball, is killed by a car. Victor is distraught at losing Sparky, his only true companion in life.
Inspired by his science teacher Mr. Rzykruski's (Martin Landau) demonstration of the effect of electricity on dead frogs, a depressed Victor digs up Sparky's corpse, brings him to his makeshift laboratory in the attic, and successfully reanimates him with lightning. Victor captures the lightning with the help of 3 flying items (an Umbrella, a Kite, and a Bat), connected with metal wires, which he lets loose in a storm. Victor had drawn the entire reanimation process on a blackboard in his attic, detailing out the entire procedure down to the most minute of details.
Seeing Weird Girl's living cat, Mr. Whiskers, the Undead Sparky escapes from the attic and explores the neighborhood. In the process Mayor Bergermeister's garden is damaged, with his flamingo mannequins toppled and his prized flower beds trampled on.Sparky returns home by the time Victor is back. He requires regular top-ups of electricity to help with his draining power reserves.
Sparky is recognized by Edgar, who blackmails Victor into teaching him how to raise the dead. The two reanimate a dead goldfish, which turns invisible due to an error with the experiment.
Edgar brags about the Undead fish to Toshiaki and Bob, which, in panic of losing the upcoming science fair, inspires them to make a rocket out of soda bottles.
Bob and Toshiaki test the rocket by strapping it to Bob's back while he was on top of a roof, which causes Bob to injure his arm as he falls down from the roof. Mayor Bergermeister blames Mr. Rzykruski at the town-hall, but Ben convinces everyone to let Mr. Rzykruski speak for himself.Mr. Rzykruski is fired due to his accused influencing and reviling the townsfolk for questioning his methods when he steps up for self-defense. Mr. Rzykruski calls the town-folk stupid and ignorant for stopping him from trying to develop the brains of their kids.The gym teacher is assigned to be the new science teacher of the class, and she has no knowledge of science. The science fair is still on, but it will be judged by someone else now.
Eventually, Edgar's fish demolishes when he tries to show it to a skeptical Nassor (who was told by Toshiaki). This incident prompts Victor to theorize that his experiments are not permanent. He consults Mr. Rzykruski who says that the first time Victor loved his experiment, but the second time he did not and that was the difference in the variables.When Edgar is confronted by Toshiaki, Nassor, and Bob on the baseball field at school, he reveals Victor's actions, inspiring them to try reanimation themselves.
Victor's parents discover Sparky in the attic and are frightened, causing the dog to flee. Victor and his parents search for Sparky while the classmates invade Victor's lab, discovering Victor's reanimation formula.Sparky, meanwhile, has ventured into the Dutch Day fair organized by Mayor Bergermeister. Mayor Bergermeister has asked his niece Elsa to be the Dutch Girl, sticking flaming candles on her cap, which Elsa said was very dangerous. Mayor Bergermeister relied on the very old fire chief for safety, if a fire broke out.
The classmates separately perform their experiments, which go awry and turn the dead animals into monsters-Mr. Whiskers holds a dead bat while it is electrocuted, turning him into a vampire cat; Edgar turns a dead rat he found in the garbage into a were-rat; Nassor revives his mummified hamster Colossus; Toshiaki's turtle Shelley is covered in a growth formula and turns into a giant Gamera-like monster; and Bob's Sea-Monkeys grow into amphibious humanoid monsters. The monsters are attracted by the bright lights of the Dutch fair and break loose into the town fair where they wreak havoc. Mayor locks himself up in a Porta-Potty.
After finding Sparky at the town's pet cemetery, Victor finds that several graves at the pet cemetery have been dug up and the corpses inside are missing. As Victor walks back home, he is met by Edgar and Toshiaki, who explain their own experiments to Victor.Victor sees the monsters attacking the fair and goes to help his classmates deal with them. But Toshiaki was only interested in making a video of the giant Shelly attacking the humans at the fair.The Sea-Monkeys explode after eating salt-covered popcorn, and Colossus is stepped on by Shelley, while the rat and Shelley are returned to their original, deceased forms after being electrocuted.
During the chaos, the town's mayor's niece Elsa Van Helsing's dog Persephone is grabbed by the mutated, and vampire like Mr. Whiskers and carried to the town windmill. Elsa and Victor chase down Mr Whiskers to save Persephone.Sparky tries to gain the attention of the humans to get help, but the towns-folks blame Sparky for Elsa's disappearance and chase him to the windmill, which Mayor Bergermeister (Martin Short) accidentally ignites with his torch.
Victor and Sparky enter the burning windmill and rescue Elsa (who was herself trying to rescue Persephone), but Victor is trapped inside the flaming windmill. Sparky rescues Victor, only to be dragged back inside by Mr. Whiskers. A final confrontation ensues, and just as Mr. Whiskers has Sparky cornered, a flaming piece of wood breaks off and impales him. The windmill collapses on Sparky, killing him again.
To reward him for his bravery, the townsfolk gather to revive Sparky with their car batteries, reanimating him once more. Persephone, Elsa's pet poodle, who has a hair style similar to the Elsa Lanchester's Bride of Frankenstein, comes to Sparky as the two dogs share their love.