Karen Idelson We’ve never been really far away from the Teenage Mutant Ninja Turtles. Since they first arrived as comic book characters in the early 1980s, there has been a steady supply of comics, TV shows, games and films that celebrate the canon of Cowabunga. And TMNT fandom, once experienced, can almost never be forgotten. Is it the masks? The pizza? The ooze that made them who they are? It’s nearly impossible to single one thing out. When lifelong Turtle enthusiasts Seth Rogen, Jeff Rowe and Evan Goldberg started working on “Teenage Mutant Ninja Turtles: Mutant Mayhem,” which arrives in theaters this August, they knew they wanted to update the characters for a new generation while also telling a relevant story. They were also interested in using a CG animation style that looked less than perfect and would remind audiences of their own doodles they might have done in a notebook while listening to a boring class lecture in high school.