Suggestions by @thecrimsonpaw

Henry Cavill

as Optimus Prime in Transformers

Seth Rogen

as Director in Teenage Mutant Ninja Turtles

Jordan Peele

as "I Think His Name is Stockman..." in Teenage Mutant Ninja Turtles

Baxter Stockman (TMNT)

as "I Think His Name is Stockman..." in Teenage Mutant Ninja Turtles

Spoiler

as "I Think His Name is Stockman..." in Teenage Mutant Ninja Turtles

The Transformers

as Next Project: in Teenage Mutant Ninja Turtles

Brad Garrett

as "Look Out, Earth!" in Teenage Mutant Ninja Turtles

Krang

as "Look Out, Earth!" in Teenage Mutant Ninja Turtles

Spoiler

as "Look Out, Earth!" in Teenage Mutant Ninja Turtles

Noah Schnapp

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

FAKE

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Jack Dylan Grazer

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

FAKE

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Tom Holland

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

FAKE

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Wolfgang Schaeffer

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Lloyd Garmadon

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Spoiler

as "The Other Ninjas..." in Teenage Mutant Ninja Turtles

Tohoru Masamune

as Oroku Saki/Shredder in Teenage Mutant Ninja Turtles

Jackie Chan

as Splinter in Teenage Mutant Ninja Turtles