If you've got a daughter or a granddaughter under 16, I can guarantee she already knows all about it. If you happen to be that mother or grandmother, remember that '60 series "Gidget," starring Sally Field? This is pretty much the same sort of thing.

In the picture, Lizzie (Hilary Duff) and some of her TV-series classmates -- Gordo (Adam Lamberg), snooty Kate (Ashlie Brillault), clueless Ethan (Clayton Snyder) -- graduate from junior high and go on a class trip to Rome. They're supervised by chunky, wisecracking Miss Ungermeyer (Alex Borstein), a kind of Rosie O'Donnell knockoff.

Once there, Lizzie is mistaken for a sultry dark-haired Italian pop star named Isabella, whose former partner and ex-boyfriend, Paolo (Yani Gellman), takes a shine to her (i.e., he takes her on a Vespa ride through the streets of the Eternal City, like Audrey Hepburn and Gregory Peck in "Roman Holiday"). He also induces her to substitute for Isabella on a big TV special. When Kate (slightly nicer than on TV) finds out, she pouts to Lizzie, "How did you get my trip?"

The move is colorful, harmless and eager to please. And did I mention, cute? Duff is very appealing, even if it is in that slightly TV-homogenized way. The shelf life of teen idols can be distressingly fleeting, but perhaps she can take heart from Field, who managed to parlay her adorableness into a serious movie career and two Oscars.

"The Lizzie McGuire Movie" doesn't have much style; Jim Fall's directorial approach is to load the film with as many close-ups of Duff giggling as he can. Still, it has an upbeat attitude and a good message about how to judge people. And look at it this way: It's a whole lot better than going to Rome with the Olsen twins.