Splinter (2018)

Splinter is the father-figure and sensei of the Ninja Turtles.

Trivia
According to an interview, the reason that Splinter looks like he's gained a few pounds, is because since there's no Shredder in the new series, Splinter has no exact reason for training the turtles, however after they learn about threats, such as Barron Draxum, he begins training the turtles more seriously.