|“||Bogs never bother me! Of course, my phantom feet never get tired!||„|
Phantasma is a phantom/ghost of about 11 or 12 years old. She has blue skin and big eyes with tiny pupils. She has white short hair with a blue streak, worn in a sideways ponytail. She wears a simple light blue dress with high heeled white cowboy boots. She is roughly the same height as Sibella.
Phantasma is loud, talented, optimistic, and clever for her age. She is good at swimming. She is the loudest, most hyperactive, and playful of the girls, and has a very high-pitched laugh that she uses usually before speaking and to express her feelings. She is also silly and wacky, but is actually smarter than she appears. She also loves to play, float, and run around.
She is good friends with all of the girls, especially Sibella and Tanis
Since she is a ghost, she is transparent and can float through many objects. She can also spin her head around like an owl.
Like Sibella and Tanis, she is undead, and thus is likely immortal.
Phantasma is the fourth girl Shaggy, Scooby, and Scrappy meet upon arriving at Grimwood's Finishing School for Ghouls. She attempts to play a piece on the organ as a form of introduction, but Shaggy and Scooby quickly retreat. Eventually, the two warm up to her and the rest of the girls, concluding that while they are truly monsters, they are actually quite friendly.
She is shown dancing ballet with Sibella and Scooby-Doo during their first gym lesson, to which she is shown to enjoy a lot.
Later in the film, Miss Grimwood and Colonel Calloway of the adjacent Calloway Military School for Boys reach an agreement about the annual volleyball game against the two schools. Realizing that they only have an hour before the game begins, Shaggy, Scooby, and Scrappy decide to give the girls on final lesson before the game begins. When the time comes for the game to start, the Grimwoods Girls have the upper hand during the beginning of the game, however Phantasma is spotted spiking the ball through the net is penalized for the action. The girls are then overpowered by the boys when two of the cadets cheat by using a remote-controlled ball to easy surpass the girls and nearly win the game, however the tide turns when Scooby-Doo accidentally shoots ketchup at the two boys controlling the ball, causing the remote-control to slip out of their hands and fire straight into Scooby's mouth, causing him to shallow it. This action unintentionally helps the girls to win the game.
Later on, the girls including Phantasma help decorate the school for the upcoming Halloween open house, in which all the girls' fathers, including Phantasma's, will attend. Her gift to her father was a composition which she wrote and played with Miss Grimwood's hand keyboard with her octopus butler on drums. It was called 'Duet for Three Hands and Six Tentacles'. When dawn begins to arrive, the girls' fathers decide to take off, but they also warn Shaggy and Scooby to take good care of their daughters or else they will face severe conquences.
The next day, the evil witch Revolta, who was spying on the girls for the entire film, set her evil plan in motion. She sends one of her spider-bats to hypnotize Shaggy into taking the girls to Barren Bog, where her assistant the Grime Creeper has set up a shack that will brainwash the girls and send them back to her castle. Phantasma is the second girl to be hypnotize after a brainwashed Winnie convinces her to enter the shack. While hypnotized, she also convinces Tanis and Elsa to enter the shack, however Sibella realizes this and attempts to escape and warn Shaggy, Scooby, and Scrappy, but is overpowered by Revolta's spider-bats and eventually hypnotized as well.
Shaggy, Scooby, Scrappy, and Miss Grimwood's pet dragon Matches all witness the girls being kidnapped and decide to rescue them, they try to persuade the Calloway Cadets to help them, but they refuse, citing their fear of monsters.
Revolta has the brainwashed girls do her bidding by clean around the castle, but reveals that her real plan is that midnight that night, she will "revoltize" the girls, a process that will turn Phantasma and the rest of the girls evil forever. Upon reaching the castle, Shaggy, Scooby, Scrappy, and Matches come across various obstacles including a mirror monster and moat monster before finally confronting Revolta. They successfully interrupt the process just in time and free all of the girls. In the process, Scooby is turned into a frog by Revolta, but manages to ruin her potion by pouring in several unnecessary ingredients, causing the potion to become unstable and begin destroying the castle. The Calloway Cadets, who had a change of heart, rescue, Shaggy, Scooby, Phantasma, and the rest of the girls just in time and fly them to safety. Revolta and the Grime Creeper attempt to chase them using flying blooms, but they are destroyed in the process by a lightning bolt caused by the chain reaction of the explosion.
After the rescue was a success, the Grimwood Girls and the Calloway Cadets celebrate their victory by having a party. Shaggy and Scooby, now officially use to being around the girls decide to stay for the rest of the semester/year, but after Miss Grimwood introduces them to new students belonging to an alien, the Creature of the Black Lagoon, and Godzilla, they change their minds and quickly leave the school.
Phantasma is last seen waving goodbye to the gang as they leave the school.