Grimm is a mutant wolf who is the leader of a gang that consisted of hyenas Jester Jim, Jester Joe, an unnamed dog, and an unnamed fox. During their crime wave, Grimm and his gang used an EMP bomb that immobilized Sgt. Swat and disabled the police's weapons. While fleeing the police in the construction site, Grimm's gang was picked off one-by-one by the Teenage Mecha Ninja Turtles. Upon Grimm hijacking a construction vehicle to fight them on even grounds, the Teenage Mecha Ninja Turtles had to work together to take down the construction vehicle and defeat him. By the time the police arrive, they find Grimm and his gang tied up. He is taken into custody afterwards.