I spent more time that I should have on this silly comic strip so y'all better appreciate it lmao... Anyways, my headcanon for the next movie is that the boys will freak out when they meet Shredder for the first time, probably catching them off guard while they're just vibing and doing random teenage stuff.
Same guy who invented pizza. He wanted to turn the mozzarella into smaller bits to let it melt and all was well for ages, until four turtles devoured all his pizza and he became their sworn villain, Shredder.