Hilary Duff in a Teen Queen Whirlwind

May 1, 2003 -- In three short years, who's changed more? Hilary Duff or Lizzie McGuire — Duff's fabulously famous on-screen persona?

Only three years ago, Lizzie McGuire hit the Disney Channel, with the title character longing for a bra. (The Disney Channel shares a parent company, the Walt Disney Co., with ABCNEWS.)

Now, the teen heroine has hit the big screen, sneaking off with Italy's hottest pop star to tour Rome on his Vespa.

‘I Haven’t Had Much Time Off Lately’

Lizzie's changing, and by extension, so is Duff, a 15-year-old who's got the No. 1 show on basic cable for girls ages 9-14. The series has given birth to eight books and a forthcoming line of apparel and accessories. Duff's debut single, "I Can't Wait," has been certified gold and she earned a reported $4 million for her work in the movie Agent Cody Banks.

But part of being a teen star is being able to portray a normal — albeit gorgeous — kid. Duff swears she's just growing up — at least the last time she checked.

"Like seriously, when I'm not working I'm doing chores or I'm hanging out with my friends," she says.

She's taken aback when reminded of her fame.

"I haven't had much time off lately and I went to the movies with my friends to see View From the Rooftop, and I saw a Cody Banks poster and a Lizzie McGuire poster and I was like, 'Oh my God!' You just forget about it, you know, until you see it and you're like, 'Wow, that's cool.'"

And What Will Gordo Think of Paolo?

The Lizzie McGuire Movie opens in theaters this weekend, with Lizzie and her friends Gordo, Kate and Ethan off on a school trip to Italy for heaping helpings of love, intrigue and gelato.

As it sometimes happens in teen comedies, average teen Lizzie soon finds she's the spitting image of Italy's pop princess and catches the eye of a Justin Timberlake-like boy star named Paolo.

"Lizzie's emotional struggles are universal," says producer Stan Rogow. "What we've done with the movie is to make the adventure bigger for the big screen and deepened those emotions."

Playing her Italian doppelganger, Duff gets to sing, something she hasn't done on her show. "I've never done too much performing, so like, I don't know, it's weird," she says.

"It was fun, though — really, really great dancers and cool outfits and the song had so much energy in it."

When Lizzie's mom, dad and annoying brother Matt get wind of Lizzie's extracurricular activities on this school trip, they make a beeline to Europe.

"It does pick up where the TV show ends off, but you don't have to have watched the TV show to know what the movie is about or to know what Lizzie McGuire is about," Duff says. "It kind of gives you a picture off the bat."

The big question is, How does Gordo (Adam Lamberg), Lizzie's best friend and partner-in-crime, take her European fling? OK, we know he can't be pleased. But, it's not like they're going out. They haven't even kissed. At least, not yet.