The Were-Rat is a minor antagonist of the Frankenweenie.
Like a real rat, Were-Rat has no loyalty to his creator.
The rat had been dumped in the garbage at school after he was killed and was found by Edgar Gore. The kids had found out about how Victor had revived his dog Sparky and Edgar wanted to see if he could do the same. Edgar took the dead rat's corpse into the school and conducted a science experiment on him. The experiment worked and the rat was reanimated. However, the rat mutated and grew bigger and stronger and walked on two feet. Edgar ran out of the school and the Gym Teacher heard him and approached the room that the Were-Rat was in. When she opened the door, she saw nothing. Suddenly, the Were-Rat jumped in front of her and she screamed. The Were-Rat chased her all the way to the science fair, which was being attacked by the other mutated animals consisting of the Turtle Monster, the Sea Creatures, the Mummy Hamster, and Mr. Whiskers. the Gym Teacher climbed up a pole and the Were-Rat snarled at her from below. Edgar was getting chased by the Sea Monsters and bumped into the Were-Rat, who chased him. Elsa Van Helsing defended Edgar by hitting the Were-Rat with a stick. Victor and Sparky ran over to help, and Sparky challenged the Were-Rat. The two animals tried intimidating the other, and Sparky made the first move by biting the Were-Rat, only to be thrown away. As Sparky got up, the Were-Rat lunged to him and bit one of his neck bolts, and the electricity surged through the rat's body. The Were-Rat was hung onto the collar and then shrunk down and became the normal dead rat again. Sparky sniffed the body of the dead rat.
- Since the other monsters are meant to bare a resemblence to the original Universal Movie monsters, the Were-Rat is meant to resemble the Wolf-Man from The Wolf Man . Ironically, Bela Lugosi, the man who played Ygor from Son of Frankenstein, also plays a part in The Wolf Man.
- In this movie, he is voiced by Dee Bradley Baker.
- The Were-Rat resembles the werewolf from The Nightmare Before Christmas.