Of course, who else would it be but The Shredder? After all, he is the ultimate villain of the turtles, introduced in the very first issue of Kevin Eastman and Peter Laird’s original comic book back in 1984. 

Originally, Shredder was the brother of a ninja who was killed by Splinter’s owner. Seeking revenge, he joins the Foot Clan and trains to become a ninja, so he could one day punish his brother’s killer. In the original comic, Shredder actually dies in the very same issue he is introduced (yeah, things were dark in the ’80s). Of course, once “Teenage Mutant Ninja Turtles” became a huge franchise, Shredder returned, time and time again. As the turtle’s main antagonist, Shredder is usually human, but he’s also been an Utrom alien controlling a humanoid exosuit (like the 2003 animated series) or a literal demon (like in “Rise of the Teenage Mutant Ninja Turtles”).

In “Mutant Mayhem,” we don’t see or hear of Shredder or the Foot Clan at any point throughout the movie’s primary running time, with the film focusing on the mutant mayhem part of the title instead. At the very end, however, during a mid-credits scene, Techno Cosmic Research Institute (TCRI) executive Cynthia Utrom (voiced by Maya Rudoph) realizes she’s going to need help in capturing the turtles, after her attempts in the first movie didn’t pan out. So she puts a call to the Shredder, who is only partially seen looking at New York City from a distance.