Fester is a minor character in the 3 Ninjas film whom ultimately attempts to help the main antagonist. He's the nephew of Mr. Brown from his unnamed sister. He and his buddies,Hammer and Marcus attempt to help Mr. Brown and Synder by kidnapping the young ninjas to cease Sam Douglas and the FBI from taking any further action against their plans.
Snyder arranges to kidnap the boys. Mr. Brown suggests to him that he knew someone who can help and has helped on several prior missions they've had and that he was a relative of his. Snyder tells Mr. Brown to make the call for him and hire his surfer nephew Fester and his friends Hammer and Marcus. During the night they attempt to kidnap the boys but their father comes home with a few of his colleagues so they're forced to withdraw the attempt. The next morning as the boys ride their bikes to school, Fester and his crew fail to grab them. The boys are at home with a sitter when Fester, Marcus and Hammer show up. Fester and his buddies jump on the pizza delivery guy and Fester poses as him in order to have a reason for entry. The kidnappers subdue the sitter and lock her in a closet. Colt sees them subduing their babysitter and their guns and tells his brothers. The boys decide if they can take care of Fester and his gang themselves, then their ninja training would be worthwhile. Using booby traps and their ninja training, they weaken the intruders. After the boys' weaken the intruders, they go to the boys' room and figure out how to lure one of their contacts who they take captive. They contacted Emily by way of attempting to imitate Rocky's voice but it successfully works with Emily half asleep and less aware. They hold Emily captive at the door. They bring Emily to the door of the study room as captive with a gun. Colt's trick with the instant diarrhea works on Hammer and Marcus leaving Fester alone with Emily. He confronts Colt and Rocky and holds them with a gun but he asks where their little brother is. Tum Tum says "Up here!" and suddenly attacks with a tennis racket hitting Fester in the head. While Tum Tum hits him, Emily faces Fester by kicking him in the shin and gives him a powerful right hook knocking him into the door frame face first and finally to the ground. Colt says "Alright Emily" who says "No sweat". After this, Hammer is subdued by Rocky and Colt and Marcus is subdued by Tum Tum. Fester, Marcus and Hammer are most likely arrested by the time law officials come to the house.