Mr. Whiskers was the hidden main antagonist of the movie and Weird Girl's psychotic albino Persian cat though he appears to be mindless. After a fluke during Weird Girl's attempt to recreate Victor's reanimation experiment, Mr. Whiskers becomes Vampire Cat where the bat half takes total control over him.
He dreams in premonitions leaving clues in the form of feces baring the first inital of one of Weird Girl's classmates from New Holland Elementary School . Mr. Whiskers can predict when bad things are going to happen; he dreams about Nassor getting into a baseball accident -- he leaves a clue in his litter box in the form of an "N."
Mr. Whiskers dreams about Victor and leaves a "V" in his cat box. He has a second premonition involving Victor and leaves a skull and cross bones; Mr. Whiskers single-handedly predicts Sparky's demise as Victor hit a home run which Sparky goes to fetch only to get run over on the way back.
He is white fluffy Persian cat.
Before his mutation, Mr. Whiskers was very quiet and nonviolent, as he would often stare at other people and animals, and would meow occasionally. Whether he was actually dreaming about them is unknown but possible. He seemed to like his owner. He appeared to like bothering the dogs though, as he comes to Victor's house and appears to taunt Sparky, leading to the dog chasing him.
After school, Weird Girl went to talk to Victor while holding Mr. Whiskers. There, Weird Girl explained her prediction that Mr. Whiskers was a psychic because he would leave droppings in the shape of a letter that would be the first letter in someone's name. She explained Mr. Whiskers did this three times before. He did it with Bob, who later fell in a hole, he dreamed of Toshiaki, the day he pitched a perfect baseball game, and dreamed of Nassor, who was knocked out while playing the umpire. Weird Girl tried to give the dropping to Victor, who refused the offer and rode away on his bike. When he left, Weird Girl shook Mr. Whiskers in the air and asked him if he would dream of her. The cat remained silent.
Something big did happen that day. At Victor's baseball game, Victor's dog Sparky was hit by a car and died. Heartbroken, Victor reanimated Sparky and kept him hidden in the basement. However, Mr. Whiskers snuck over to the house and started to taunt Sparky. Sparky retaliated by chasing the cat to Mr. Burgermeister's lawn, where Mr. Whiskers climbed up the house, but not before knocking down Burgermeister's plastic flamingos.
After Sparky was discovered, the other children immediately tried to bring their dead animals back to life. Unfortunately, their experiments went wrong and the dead animals were mutated. Toshiaki's turtle became the Turtle Monster, Edgar Gore's dead rat became the Were-Rat, Nassor resurrected the Mummy Hamster, and Bob created the Sea Creatures. Weird Girl decided to resurrect an animal as well, and Mr. Whiskers brought a dead bat to her and convinced her to resurrect that. Unfortunately, Mr. Whiskers began playing with the bat when the lightning struck, so her experiment went wrong too, and Mr. Whiskers was electrocuted. When Weird Girl checked to see if he was alright, Mr. Whiskers grew fangs and his fur became darker, confusing Weird Girl. As his owner looked on, Mr. Whiskers twirled around and became thinner and larger. His tail and legs extended, and as he sat up, his neck extended as well. Going down on his front legs, Mr. Whiskers sprouted bat wings in front of Weird Girl. With no memory of his past, the mutated cat destroyed the room and flew out the window, followed by Weird Girl.
- Mr. Whiskers is constantly confused to be the hidden secondary and tertiary antagonist. This is not true as he drives the plot, has bigger plans, and is the most villainous character.