Firstly, Jeff Rowe wanted to relate that casting his four lead actors was a massively long process, and that he and the film’s casting agents listened to hundreds of voices before finally settling on the actors they did. The studio, perhaps naturally, wanted to include bankable, recognizable stars in the lead roles, something Rowe definitely didn’t want. Luckily, there were a dozen other supporting players that could fulfill the studio mandate. Rowe said:
“[D]oing the film was contingent on casting real teenagers in the roles, and I think it was just understood very early on that this will be four unknown actors. We’re going to do a big casting search. We worked with Rich Delia who was so good at this and brought us hundreds of people and we found Nick, Brady, Micah, and Shamon, who are all amazing. But I think beyond that, the studio wanted some names in there and some marketability, so we went bigger on all of the other roles.”
The cast also includes Jackie Chan as the mutant rat Splinter, and Ice Cube as the film’s villain. Rose Bryne, Paul Rudd, John Cena, Hannibal Burress, Giancarlo Esposito, Post Malone, Maya Rudolph, and producer/co-screenwriter Seth Rogen all appear in smaller roles, many of them playing additional mutant animals.
Once that was clarified, Rowe moved on to address the potential crisis of Cantu, Noon, Brown, and Abbey developing deeper voices. Rowe was unconcerned, knowing that puberty can play cruel pranks on a child, and bodily growth is sometimes unpredictable.