last night, Avril Lavigne wore a skirt on the red carpet for the first time. "A little black mini from my closet, with my buckle boots," she says. The occasion was the awards show for MuchMusic, Canada's version of MTV, and at the after-party she sat in the VIP section, trying to have a real conversation with the guys from Nickelback, which proved difficult. People kept walking by, rubbernecking, she says. "I honestly felt like I was in a zoo--'Look at the monkey!'"

So she did what a 20-year-old rock star whose 2002 debut CD sold 14 million copies could reasonably be expected to do. "I partied really hard and got wasted," says Lavigne, who, thanks to media labeling as a petulant punkette, is unlikely to be busted for pretending to be a good girl--though in many ways she is. After the bash, she returned to her condo in Toronto with just enough time to throw some things into a suitcase for a 6 A.M. flight. She was off to Los Angeles to perform "My Happy Ending" from her latest CD, Under My Skin, for Jay Leno and more than 6 million viewers.

Padding around in her stocking feet that evening, Lavigne looks no worse for crossing three time zones and working all day. "I have lots of energy," she says, entering a suite at the Four Seasons with drinks in both hands. Tonight, however, the refreshments are a bottle of Super-Green, with "grasses and plant enzymes that taste kind of gritty," and a goblet of fizzy pink vitamin C. Popping out the transparent orthodontic retainers she wears on her teeth, she admits...