Watch the Teenage Mutant Ninja Turtles and Mo-Cap Actors Side-By-Side (Exclusive)

In the Teenage Mutant Ninja Turtles movies, the reptilian heroes are the result of a crazy science experiment. In reality, the complex computer animation that creates the turtles involves spandex motion-capture suits, face cameras, human-sized “turtle” shells, and four versatile actors. Take a look at the side-by-side “before” and “after” performances of Leonardo (Pete Ploszek), Michelangelo (Noel Fisher), Raphael (Alan Ritchson), and Donatello (Jeremy Howard) in Yahoo Movies’ exclusive behind-the-scenes video from Teenage Mutant Ninja Turtles: Out of the Shadows (in theaters now).

Related: What Original ‘Teenage Mutant Ninja Turtles’ Star Elias Koteas Told Us About Playing Casey Jones Back in 1990

Outfitted with complex mo-cap suits, the actors playing the turtles in Out of the Shadows shot their scenes on location in New York City, side-by-side with human characters played by Megan Fox, Will Arnett, and Stephen Amell. The detailed animation captured both their body motions and tiny facial expressions — though as Howard, who plays Donatello, explains in the video, “I know that if I’ve got my mouth hanging wide open or make this kind of a face, it’s going to look weird on the CG turtle. It’s kind of a fine line between what you’re feeling as an actor and what’s going to transfer well onto that CG face.” Fox, who plays reporter April O’Neil, says that she “stopped seeing the mo-cap suits two days into the first movie [2014’s Teenage Mutant Ninja Turtles]” because the actors’ personalities “shine through so strongly.” In a separate interview with Yahoo Movies, she also mentioned a fringe benefit of working with motion-capture actors. “They’re super hot guys,” Fox told us. “So I don’t see those dots or those suits. They’re Spandex suits, by the way. So it ain’t a bad situation.“

Watch Fox talk about her blonde wig in ‘Out of the Shadows:’