Teenage Mutant Ninja Turtles: Mutant Mayhem heavily changes a lot of what fans know about the Ninja Turtles. From how the teenage turtles act to the world around them, things are quite different from the franchise's other continuities. This can be seen in how the movie's secondary antagonist references a classic species from previous shows and comic books.
Source:https://www.cbr.com/tmnt-mutant-mayhem-changed-utroms-better/