These are the villains that appeared in the show.
The evil leader of all Annunakki and the main antagonist of the whole series.
The Freak of Crystal Cove is one of the shows main antagonists along side Professor Pericles. He threatened The Original Mystery Incorporated to give up mystery solving or their families get hurt. 20 years later he resurfaces to see Fred Jones ignore Angel Dynamite's warning about him and then he pursues the gang for the Planespheric Disk and pieces to the cursed treasure. After fleeing out of The Caves, he is apprehended by Fred and as he unmasks the Freak, it is shown to be the Mayor. The Mayor confesses that he was never Fred's father all along.
The Slime Mutant is the first villian that the gang encounters in "Beware the Beast from Below." Its appearance was a tall green monster who smelled like Fruitmeyer's dessert. It is revealed at the end that the monster was Professer Emmanuel Raffalo, a Crystal Cove High teacher who used a secret door in Fruitmeyer's backroom to get into the sewers to drill a passage to get into the bank secretly.
Grady, Greta, and Gunter Gator, or the Gator Family appeared in Creeping Creatures. They were scaring people away from Gatorsburg to make sure no one found out that they were making faux gator products. Greta and Gunter run the hotel and Grady is a mechanic.
It kidnaps people at a volley ball tournament.
he paralyzes people dreesed as pirates at the medevil fair
The Humongonauts were the twin brother Max Minner and Jax Minner. They used the disguises to attack places that were owned by their brother.
The Frighthound was a creation the Mrs. Wyatt invented to tear the gang apart and let her son Jason be with Velma, but when she saw that they were blaming Jason for being the creator of the Frighthound, she decided to kill them all.