Emma Watson's used to transformation. But playing an American teenager? That's a bit of a stretch.

Watson cut her teeth on acting by playing the studious, plucky Hermione Granger in the "Harry Potter" film series, but her first role after Potter is another world for her entirely. In "The Perks of Being a Wallflower," based off the cult-novel of the same name, she plays an American teen who's part of a clique of hip outsiders at a Pittsburgh school.

The 22-year-old British actress said playing the role gave her a taste of a whole different life considering her cloistered upbringing on the set of the Potter franchise, in which she was cast at age 9.

"It felt pretty exotic to me. It really did. It was a very voyeuristic experience," Watson said in an interview Sept. 9 at the Toronto International Film Festival, where "Perks" played ahead of its U.S. theatrical release Sept. 21. "Getting to go to Friday night football and Olive Garden, school dances and all of that stuff. That was really another world to me."

"Nobody has ever seen her in this kind of role-and with an American accent," costar Nina Dobrev said at the movie's Toronto International Film Festival premiere, adding, "She finished one chapter of her life, cut off her hair and embraced this new beginning. I think everyone is going to be very pleasantly surprised."

After a decade as Hermione, Watson aims to give "Harry Potter" fans a taste of what she can do outside the world of witches and wizards.

"I hope what they can see is that I am able to transform, that there are other sides of me that perhaps they haven't seen yet, and that they might allow me a little bit of room," Watson said. "I mean, just doing American really is different. People have said to me that they keep forgetting it's me when they see the movie, which for me is more than enough. That's a success in itself for me, really."

Watson, Logan Lerman, and costars Mae Whitman, and Ezra Miller all stripped down to skimpy clothing for dancing scenes that took place during screenings of The Rocky Horror Picture Show.

"It doesn't show but I was absolutely terrified," Watson admitted.

"I watched her throw down so hard in every capacity," said Miller, who plays an out gay student secretly dating the school's football star (Johnny Simmons). "She can get down-and Wats gets down!"

Watson said at the premiere that growing up in a bubble of celebrity has left her feeling like a kid when it comes to many things.

"There are some parts of me that feel very old, and then there are other parts of me that are, like ... I have a sense of my own arrested development," Watson said. "There are some parts of me right now that are probably going through adolescence."

Her work ethic is pretty grown-up, though. While attending Brown and working on last year's "Harry Potter" finale, Watson squeezed in a small role in the Marilyn Monroe drama "My Week with Marilyn."

After "Perks," she co-starred in Sofia Coppola's 2013 release "The Bling Ring," playing one of a group of celebrity-obsessed Los Angeles teens who burgle the homes of Hollywood stars. Watson also has a cameo role in Seth Rogen's upcoming comedy "The End of the World," playing a version of herself alongside other stars coping with the apocalypse during a party at James Franco's place.

Watson came to Toronto for the "Perks" premiere on a break from her next project, co-starring with Russell Crowe, Jennifer Connelly and Anthony Hopkins in director Darren Aronofsky's biblical epic "Noah."

Adapted by director Stephen Chbosky from his own novel, "Perks" casts Lerman as a deeply troubled high school freshman who falls in with a crowd of smart, nurturing seniors dealing with plenty of issues of their own. Watson's Sam becomes his dream girl, an old soul with a dark past herself earlier in her teen years.

Chbosky's novel has been a cult favorite with disaffected adolescents since its release in 1999. Part of that legacy is spelled out neatly on the book itself: "MTV Books."

"The Perks of Being a Wallflower" is out in theaters Sept. 21.