Olivia Thirlby, sidekick from "Juno," on "The Wackness" and other teen roles

Olivia Thirlby has been one of the best things about the movies she's appeared in, first as the wry best friend in "Juno" and then as a quirky high-schooler in David Gordon Green's dramedy "Snow Angels." Thirlby, 21, claims even more of the spotlight as a teen femme fatale in "The Wackness," about a young man coming of age in 1990s Manhattan.

Q: Your most memorable roles — actually, all your roles — have been teenagers. Is that constraining?

A: The age of a character doesn't bother me. I would play a 14-year-old if it was a great part. It's more about the dimensionality of the character. There are some scripts that, even though they're only 100 pages long, you feel like you really know a character just from what they say and do. If a script has that, it doesn't matter what someone's age or situation is.

Q: You've said that your role as Stephanie in "The Wackness" was risky for you. How so?

A: Some of the bikini and the sex scenes was territory that I did not think I would cross into. In the past, I've turned down roles with sex scenes, and I won't do nudity. I didn't do any in this film. But even the bikini — I'd kind of sworn off bikinis for life. They were kind of evil in my mind. I never had a positive experience involving a bathing suit.

Q: How did you get over that?

A: I started running a lot. I would read the script right before I went out running, and I would flip open to the beach scenes and I would try to picture them in my head and the image would kind of propel me out the door to go push myself really hard. I wasn't born with what I deemed a bikini body, and it's rewarding now to look back and I feel good about my bikini body in "The Wackness."

Q: I was surprised to learn that you have extensive training in Shakespeare, both in New York and London.

A: I can't wait to do Shakespeare again. I'm ripe for Juliet! I played Helena when I was a senior in high school, probably the most fun I've ever had. I am looking very forward to being old enough to play Beatrice. I've kind of dabbled with Ophelia, I love Portia in "Caesar." I think possibly my favorite thing about Shakespeare is that he writes the most bad-ass women characters.