Years ago on ''Saturday Night Live,'' Joe Piscopo's Frank Sinatra referred to Paul McCartney as ''that Beatle kid -- you know, the one who looks like a broad.'' You wonder how he would have described Lance Bass, the 'N Sync chorus boy who stars as a lovestruck Chicago ad writer in On the Line. With his sweetly grinning fluffy-cheeked face, Bass resembles nothing so much as the slightly less masculine sister of k.d. lang. He's so harmless you practically want to turn him into a throw pillow, yet there's no denying that he plays to his tween-girl audience with the same ingenuous instinct on screen that he shows on stage.
In ''On the Line,'' Bass meets his cutie-pie soul-mate (Emmanuelle Chriqui) on the L train. After failing to get her name or number, he plasters the town with please-call-me handbills, which is enough to turn him into a media sensation. Fellow 'N Syncer Joey Fatone is also on hand as a roots-blond ''punk'' who plays Mutt to Bass' Jeff. ''On the Line'' would like to be ''Serendipity'' for the Oxy-and-Skechers set, but it feels more like the worst movie Michael J. Fox never made.