Previously just a girl in America's best new-wave ska band, No Doubt, the platinum-blond Californian Gwen Stefani emerged as a trendsetting clotheshorse, Vogue cover girl, and, oh, yeah, huge solo pop star in 2005. It's all thanks to the delirious, '80s-themed confection Love.Angel.Music.Baby., which has sold more than 3 million copies since arriving in stores last November.

''I was able to indulge my cheesiness and the theatrical side of myself,'' says Stefani of her solo debut, which has spawned five hit singles and videos. ''I didn't feel like I had to make something that was serious. If you listen to the lyrics and music, it's not a serious album! It's just pure fun.''

Few songs in 2005 were more joyous — and wonderfully frivolous — than Stefani's biggest track, ''Hollaback Girl,'' the best white-girl hip-hop tune since Blondie's ''Rapture'' and the best-selling digital download of all time. ''I was finished with the album, but I knew in my heart that I didn't have my attitude song,'' she says. A mere 10 minutes later, Pharrell Williams and Stefani sat down together and cranked out the uncharacteristically feisty track. ''I never got in any girl fights in high school,'' she says, laughing. ''I'm a lover, not a fighter.''

Stepping away from her band of 17 years was a major change for the 36-year-old Stefani — one that proved both welcome and difficult. ''There were some perks of being a solo act,'' she says. ''Interviews are easier on my own. If I want to talk about lipstick or fashion or girly stuff, I can.'' But she missed the backup while organizing and headlining a theatrical, highly choreographed two-month stadium tour. ''That was one of the hardest tours of my life,'' she says. ''Every night I would just go to my bus and collapse and instantly pass out.'' Stefani already has enough material for another full solo album, but after such a jam-packed, exhausting year, she's not exactly itching to get to work on recording it (look for a new Stefani disc in late 2006). ''Come January,'' she says, ''I'm just gonna hibernate and eat pizza and sleep.''