The last time Toni Collette packed on the pounds for a movie role, she was 22 years old and starring in 1994's Muriel's Wedding. Eleven years later, Collette tried a similar stunt for In Her Shoes, a dramedy filmed in Philadelphia and opening today in area theaters. But this time around, the Sydney-born actress actually had a harder time putting on the 25 pounds than taking it off. "My character loses weight when she gains self-confidence and happiness in her life," says Collette. "So they gave me 11 days off to run my butt off, literally. I must have done a good job because at one point, (director Curtis Hanson) said, "You're losing too much weight. Just stay where you are and start eating again.' Well, let me tell you, the restaurants in Philadelphia are the best and I know because I've eaten at all of them."

That said, Collette swears she's never doing "the weight seesaw thing" again. "I would really prefer never to put on that much weight because it's hard on the system, especially the older that you get," she says. In the movie, Collette and Cameron Diaz play polar opposites who happen to be sisters. Collette is Rose, a Princeton-educated lawyer with no time for a social life, while Diaz is Maggie, a party girl so flaky she can't hold a job. After a nasty falling out, the two sisters eventually reconnect, thanks to their long-lost grandmother (Shirley MacLaine). "All three of these women are just surviving," notes Collette. "They're all living with the loss of either a parent or a child. I think that Rose and Maggie have developed this co-dependency. They're kind of forced to look at who they are as individuals instead of just, "I'm the needy one' and "I'm the one who needs to help the needy one.' I think this makes the movie very rich and real and special."

Collette admits she got hooked on the project as soon as she read Susannah Grant's screenplay, which is based on a best-seller by Jennifer Weiner. Sweetening the deal for Collette was director Hanson, the man who has made such critically acclaimed films as L.A. Confidential, Wonder Boys and 8 Mile. Collette has appeared in a variety of movies, including The Sixth Sense, for which she earned an Academy Award nomination, as well as About a Boy, The Hours, Shaft and Velvet Goldmine. But working with Hanson is near the top of her list of great experiences. "Curtis Hanson is the best director that I've ever worked with, hands down," she says. "He's a very wise man and he still has the wonder of an 8-year-old at the same time. He hasn't lost his lustful eye."

Did Collette enjoy working with MacLaine? "Abso-freaking-lutely," she whoops. "Are you kidding me? She's a living legend. I've seen her in a million movies and now that I know her, I admire her even more. I think that she's a really great, down-to-earth lady who's very opinionated and strong and warm and funny." Collette is just as enthusiastic about Diaz. "She's an easy-going, open, beautiful person," notes the actress. "There are some films where it just feels like it's really meant to be and this was one of them. We all just really went for it and really loved the experience."