There was one scene in the final trailer for It: Chapter Two that may have puzzled you, especially if you are a fan of the original Stephen King book that this second installment is based on. Around the halfway mark, Adult Bill (James McAvoy) is lost in a hall of mirrors, which is something that does not happen in King's novel. The scene is a completely added invention by director Andy Muschietti, and it happened as a result of him drinking tequila with McAvoy.
In and interview with Entertainment Weekly, McAvoy talks about this departure from the book, and how it came to be. He was enjoying some tequila one night with Muschietti, and the idea came out.
As McAvoy says, “We were missing a vital story beat for Bill where he dealt with his guilt that he caused his brother’s death. I said to Andy, 'What can we do?’…and literally in 50 minutes, he invented a whole new sequence. It was never in the script, and it isn’t in the book. It’s brilliant.”
The guilt is likely boiling over for Bill, because after he left Derry he forgot all about the horrors he experienced in the first movie, and pretty much forgot about the death of his brother as well. Bill's memories come roaring back in this film, as does Pennywise, the terrifying clown-phantasm that he and his friends "defeated" by beating him with poles in the first film.
McAvoy was already a fan of the book, having read it when he was much younger. He didn't find it very scary then, but reading it as an adult was a different experience. “When I reread It as an adult for the film, I actually had nightmares about Pennywise in a way that I never did as a child,” McAvoy says.
“He’s writing about a small American town, he’s writing about death, he’s writing about growing old, growing up," he adds. "And the movie is very much about that. You could argue the first movie is as much Stand by Me and Goonies and all those things as it is a horror movie.”
McAvoy was Muschietti's first choice to play the role, and it was Jessica Chastain (Adult Beverly) who had previously worked with Muschietti on Mama that put then together...she had just worked with McAvoy on Dark Phoenix. For McAvoy, it was all just rumors and wishes, until it wasn't.
“You hear things like that a lot in your career from various different people, and it doesn’t always necessarily come through,” McAvoy says, before quoting some wisdom he received from another actor earlier in his career: “Don’t believe you’ve got the job until you see yourself on screen at the premiere."
It: Chapter Two comes to ruin dreams and make you want to destroy your mirrors on September 5th.