Kevin Clash should make an appearance
 

He is mainly known as the voice of Elmo on SESAME STREET, and had voiced Splinter in the 1990 TMNT film.


It'd be cool if he made a guest appearance on the show, though I don't know who he could voice.

He doesn't work much these days from what I understand, but I'd always welcome his return to the franchise. He's a talented guy, & his Splinter was amazing. They should get as many Henson-TMNT alumni as possible, even Sam Rockwell. It's great that we have Robbie & Corey as it is, though.