Poor Mariah Carey. Even after the Feb. 15 release of pop tart Britney Spears's debut feature, Crossroads, Glitter still isn't likely to be replaced as comics' favorite punch line. In fact, Spears rocks in the romantic comedy, at least according to castmate Justin Long (better known as the adorably awkward Warren Cheswick on Ed).

"I think she's going to surprise a lot of people with her acting ability," the 23-year-old tells TV Guide Online, adding that the two of them did a lot of ad libbing — quite a feat for a movie virgin. "I was certainly surprised."

Long probably isn't paying lip service to his leading lady's talent, either. If anything, since he gives her her first silver-screen kiss, he is more anxious about how his own performance turned out than hers. "Luckily, the scene called for a lot of tension on my part," he laughs. "But really, I was amazed at how normal she was. There's no hint of diva-ishness about her.

"After 10 minutes, I completely forgot who she was," he adds. "She took on this whole new character for me [as] just this really cool girl."

Although, of course, she isn't merely "really cool," but totally hot with the kids, her co-star doubts that he soon will be inciting the kind of riots that teenage girls usually reserve for Spears's beau, Justin Timberlake. "I play Britney's lab partner, so it wasn't really a hunky role, unfortunately," he sighs. "I have to spend some more time at the gym before I do that."