Despite the challenges of playing a character with dissociative identity disorder, James McAvoy was thrilled to reprise his role of Kevin Wendell Crumb and revisit all his favorite characters in M. Night Shyamalan’s Glass.

As introduced in 2016’s hit film Split, Crumb’s multiple personalities develop after his father disappears and mother starts abusing him.

Of the 24 different personalities he plays as Crumb in Split and its sequel Glass, McAvoy especially loves transforming into Miss Patricia, a controlling matriarch.

“She’s real kinky, and devout, and pious, but kind of longing to be touched at the same time. Which is sort of achingly sad and dead fun to play,” McAvoy tells PEOPLE.

Additionally the Scottish actor enjoys jumping into Crumb’s other main identity, Hedwig, who identifies as a nine-year-old boy.

“He just doesn’t really recognize barriers or boundaries, and it allows him to be pretty inappropriate with anybody and everybody,” he says of Hedwig.

To prepare his body for the film, McAvoy revealed the grueling work it took to bulk up.

“I had a really good trainer, who made me eat like a beast, and made me lift a lot of weights,” he says.

The movie also reunites Bruce Willis, 63, with his Unbreakable costar Samuel L. Jackson (Elijah Price).

In addition, Unbreakable alums Spencer Treat Clark (Joseph Dunn) and Charlayne Woodard (Mrs. Price) will also be back, as will Split‘s Anya Taylor-Joy (Casey Cooke). Sarah Paulson is a new addition to the cast, as Dr. Ellie Staple.G