Giant mutant turtles are enough for me. There's no need to add aliens. A cartoon series is one thing, cause you can flesh it all out. However, in a movie they should just stick to the main focus. It's why the original two movies were so successful IMO.It was actually pretty awesome to see, because Leo chopped off his head to end the series and we assumed he was dead. Then he comes back next series and you're like sayeth whatttt and you find out he was basically like an evil version of Krang from the original series, using the identity of the Shredder.