The 2007 Toronto Party Circuit

The circus came to town when Sienna Miller hosted a party at Canadian department store Holt Renfrew to introduce fashion fans north of the border to her new Twenty8Twelve line. Stilt-walkers and fire-jugglers lined the red carpet entrance and inside it was an equally wild scene. Behind the plush red velvet curtains of the VIP room, ringmaster Miller played host to celebrity friends like Sean Penn, Maggie Grace and Liv Tyler. Emile Hirsch eyed the super-sweet buffet table offering sugary delights like mini ice cream cones and oversize lollipops. "We love the Oliver Twist era, so this circus theme ties in very nicely," said Sienna?s sister and co-designer, Savannah Miller. "Sienna and I are inspired by Dickensian London and all that kind of backstreet weirdness that went on at the time."

Everyone in Toronto is buzzing about the brand new Hazelton Hotel, but the appearance of Kate Bosworth and Sigourney Weaver only managed to up the glam factor. The duo attended In Style's intimate dinner party for their new film, The Girl in the Park. Bosworth looked effortlessly fabulous in a chic short frock by an up-and-coming designer, Preen. "It's an English label. They’re kind of underground and they don't tend to lend out clothes," she said of her ensemble. Bosworth was just as excited to talk up her movie. "I love this film and the cast," said the actress, whose co-stars include Keri Russell, Alessandro Nivola and Elias Koteas.

-With reporting by James Patrick Herman, Vivian Vassos and Suzanne Zuckerman

"We're so thankful to In Style for this lovely dinner. Otherwise we would have been eating peanut butter and jelly sandwiches tonight," said Sigourney Weaver at the bash for The Girl in the Park. Instead, guests dined on grilled strip steak, Alaskan black cod and bucatini with veal ricotta meatballs prepared by renowned celebrity chef Mark McEwan, who runs the Hazelton hotel’s One restaurant. Toronto's impressive cuisine was also on the mind of first-time director David Auburn. "Today I had the best brunch of my life here," he said. "And I live in New York!"

"I was in the cab like this," said Emily Mortimer, taking on the pose of a stiff robot to signify how difficult it was to move around in her glamorous Vivienne Westwood dress at the In Style party for Lars and the Real Girl, held at Brassai bistro. Asked to give her own review of the finished film, the humble actress played it coy. "I've already seen it once so I'm not going to do the neurotic thing," Mortimer said of the flick, about a young man who forms a romantic relationship with a synthetic doll.

Naomi Watts

revealed that her life imitated her art during the filming of Eastern Promises, which premiered at the festival on Saturday night. "I started shooting just before I found out I was pregnant," Watts, who plays a mid-wife in the film, told reporters. While the new mom left tot Alexander at home to join Viggo Mortensen and Maria Bello at the after-party-held at hot spot Cheval-her latest real-life role has made her more of a homebody. "Life has changed dramatically, now it’s all about the baby," she said. “You can’t be as spontaneous.”

Though he's not screening his directorial debut, Gone Baby Gone in Toronto, Ben Affleck was one busy guy at the festival, showing up at a surprise screening of his buddy Matt Damon’s flick, Running the Sahara, which centers on raising awareness about the clean water issue in Africa and the non-profit organization, H2O Africa. When Affleck was asked by reporters if he'd ever work with Damon again, he answered with a definite yes. But when pressed by for details he simply stated, "If I told you, I'd have to kill you."

Matt Damon

also teamed up with his Ocean's Thriteen co-star Don Cheadle to catch the premiere of Brad Pitt's The Assassination of Jesse James by the Coward Robert Ford at the Elgin Theatre. The busy Damon also hosted the second annual OneXOne gala ito fight poverty and preserve the lives of children around the world, where he was agained joined by Cheadle and Duchess Sarah Ferguson. Ben Affleck helped Damon auction off items like a tennis lesson with Andy Roddick and a trip to South Africa. Matt and Ben kept up their best buddy schtick to entertain the bidders. "People say: 'You're a lot taller than I thought,'" Matt quipped about how the fans react to Affleck. And what do they say to Damon? "People say, 'You're a lot smarter than I thought,'" Affleck quipped.

"I will do a private concert in your house!" offered Wyclef Jean to the crowd of bidders at Matt Damon's One X One event, held at Toronto?s glamorous new opera house. Jean then showed off what the winner could expect when he backed up Shakira?s hip-shaking performance, which got Petra Nemcova into the spirit of giving. "I will cook!" the model volunteered. "I will bake strudel."

Before the premiere of their film, The Jane Austen Book Club, co-stars Maggie Grace and Maria Bello attended the Sony Pictures Classics party at Toronto hot spot Michelle's Brasserie. "We all bonded on such a huge level," said Bello of filming the romantic drama, which will hit US screens in November.

After hitting the launch party for Sienna Miller's new Twenty8Twelve line, Hilary Duff provided the entertainment when she performed at MuchMusic's Star! Schmooze at department store Holt Renfrew. The pop star-who recently wrapped filming on a new movie with John Cusack-hit the corner of Queen and John Streets for an outdoor concert attended by thousands of fans.