The Grim Creeper is a mutant plant creature and the minion of Revolta.
Physical appearance: The Grim Creeper is dark green and looks like an Idaho potato with a red eye, and has light green tentacles for arms and hands.
Personality: he Grim Creeper was very rude and cruel and seemed to enjoy helping Revolta capture the girls.
Powers and abilities: He could control other monster plants like the Venus Spy Trap, which could send him images of what it saw.
History: Scooby-Doo And The Ghoul School: As the minion of Revolta, Grim Creeper was sent to capture the girls. When he succeeded, Shaggy Rogers, Matches, Scooby-Doo and Scrappy-Doo all went out to find the girls. During a storm, Grim Creeper watched and he saw the mightiest monsters coming to Grimwood's school such as Count Dracula, Frankenstein, a werewolf, a mummy, and a phantom. After Shaggy was trapped in the mirror, an evil version of Shaggy emerged, but Matches just breathed fire on him and the real Shaggy got out and his evil version got back into the mirror.
Grim Creeper was pouring the ingredients to turn the girls into evil ones and grabbed Scooby by the tail and Scrappy, Shaggy, and Matches saw Scooby fall and they fell with him into a huge well of water. Grim Creeper told them that they were being watched by a giant Well-Dweller. After dealing with the Well-Dweller and getting out of the well, Revolta had completed her formula and started to 'Revoltize' the girls. Scooby and Shaggy slammed straight into Tanis and Winnie Werewolf and knocked off the helmets causing them to turn back to normal. Tanis took the helmet off of Sibella and Elsa Frankenteen got out by herself by unknown means. One girl was still stuck. Revolta turned Scooby into a toad and a spider bat saw Scooby as a toad and it tried to eat Scooby. As a result of the chase, some extra ingredients fell into the formula and Phantasma turned back to normal.
Grim Creeper grabbed Scooby and the others, but Matches breathed fire on him and he failed to stop them. Grim Creeper and Revolta both get hit by the explosion in their brooms and they fall.