Is there a reason why they didn't use Krang in the TMNT movie that came out last year? I can see not using him in the live action films of the 90's, but it would have made sense to incorporate him into a CGI atmosphere. Definitely would have pleased this hardcore Ninja Turtles fan.
Krang, Bee-Bop, and Rocksteady are characters that will only appear in the original TMNT animated series. Krang was just based on the U-Trons, the alien race that appears in the comics. In the 2nd movie, the scientist guy was going to be revealed as an U-Tron, but they thought they people would think that he was Krang.
They could've brought Rick Moranis out of hiding to play Baxter.