James McAvoy goes full Beast mode in Glass clip

James McAvoy got in extremely muscular shape to reprise the role of Kevin Wendell Crumb (and his many personalities, including "The Beast") for M. Night Shyamalan's trilogy-concluding superhero film, Glass (out Jan. 18).

"I realized that if M. Night Shyamalan's world is suggesting that the Marvel world, and the DC worlds, and all the comic book worlds, they grew up out of something that is possibly true, then the aesthetic of those worlds should maybe come from something that is possibly true as well," says the actor. "So, I thought, If I'm going to run about with my shirt off for half the movie I've kind of got to buy into the comic book superhero aesthetic a little bit, you know. Which I didn't necessarily have to do massively for the first movie, because, really, I only had my shirt off for two minutes at the end. I was in good shape, and I made sure I was toned and all that stuff, but I thought I'd better actually get bigger this time.

"So, yeah, I trained for about five months, and ate a ton of food and this guy Magnus Lygdback, got me into the biggest and muscliest shape I've ever been in. There are guys out there that are much bigger and musclier, but for me, I did real good."

A sequel to both 2000's Unbreakable and 2017's Split, Shyamalan's film co-stars Bruce Willis, Samuel L. Jackson, Anya Taylor-Joy, and Sarah Paulson.

Exclusively watch a scene from Glass featuring McAvoy and Willis above.

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• Samuel L. Jackson unleashes the Beast in new Glass trailer