Scooby-Doo,
Shaggy, and
Scrappy-Doo are on their way to Miss Grimwood's Finishing School for Girls, where they have been hired as
gym teachers. However, once there, they find that it is actually a school for daughters of paranormal beings. The pupils include Sibella, the daughter of
Count Dracula; Elsa Frankenteen, the daughter of
Frankenteen Sr.; Winnie, the daughter of the
Wolfman; Phantasma (usually called Phanty for short) the
ghostly daughter of a phantom; and Tanis (
named after an Egyptian city), the daughter of the Mummy. Other residents include a disembodied floating white hand; an octopus
butler; a two-headed shark that lives in the school's moat; Legs, a spider that helps with the upcoming
volleyball match; Miss Grimwood, the headmistress; and her diminutive pet dragon Matches. Frightened by this, Shaggy and Scooby are initially hesitant, but they ultimately agree to stay as gym teachers, as the girls quickly take a liking to them. At the annual volleyball match against the boys of the neighboring Calloway Military Academy, the boys rig the volleyball with a remote control in the hopes of cheating to win. However, Scooby accidentally swallows the remote, which allows the girls to win instead. The girls' fathers then come for an open house party on
Halloween night. Although Scooby and Shaggy are extremely fearful of being trapped in a house full of ghosts and monsters, the fathers are friendly and polite, and the party is a success. Before leaving, the fathers warn a terrified Shaggy and Scooby not to let any harm come to their daughters, lest they face severe consequences. A power-hungry witch named Revolta and her minion the Grim Creeper then plan to kidnap the girls and convert them into her slaves. She starts by hypnotizing Shaggy into taking the girls on a field trip to the Barren Bog. Matches wants to come along, but is told to stay. The Calloway Cadets are also at the bog on a hike of their own and get stuck in quicksand, but are saved by Elsa and Tanis. Meanwhile, Revolta's spider bats slowly capture the girls one by one, as Revolta brews a potion that will turn the girls evil forever at the stroke of midnight. Having figured out what's going on, Scooby, Scrappy, Shaggy and Matches, who catches up with them, all head for Revolta's castle. Along the way, Scrappy tries to convince the Cadets to join them, but the boys refuse, believing that the girls stole the volleyball match. Arriving at the castle, the gang faces an evil Mirror Monster that can change its shape to look like evil versions of those who look at its mirror, a giant Well Dweller, and Revolta herself. When the clock strikes midnight, Revolta gives the girls the potion through hairdryers, which instantly takes effect. However, Scooby and Shaggy interrupt the process and accidentally reverse the potion's effect. Elsa then throws Revolta's wand into the potion, which causes it to explode. The Cadets, having felt remorse for treating the girls poorly and respecting them for saving their lives, arrive in a pedal power helicopter and fly everyone to safety, as Revolta swears vengeance. Soon afterward, the Cadets and the Grimwood Girls throw a party celebrating Revolta's defeat and everyone's heroism. Despite being well liked by all their students, Shaggy and Scooby run away in terror when three new monsters – an
alien, the
Gill-man and
Godzilla – enroll their daughters at the school for the following year. As they leave, they see the girls and Matches waving goodbye. Shaggy, Scooby and Scrappy then give them a last werewolf howl before driving off into the night. ==Voice cast==