No one can accuse Jamie Kennedy of not having the white rap thing down. In ''Malibu's Most Wanted,'' he plays Brad -- or, as he likes to be called, B-Rad -- a rich Jewish kid from Southern California who fancies himself a stone-cold gangsta. ''I'm da shiznit!'' says B-Rad, who is presented as a lame Eminem wannabe, a privileged dork in a puke-green tracksuit thrusting his fingers at perplexed boutique cashiers. He's incapable of uttering a normal sentence, whether he's telling his politico father, played by Ryan O'Neal playing William Shatner, to ''Pound it!'' (that is, his fist) or passing someone a copy of his vanity CD with the request ''Pick mah steel up!''
Yet Kennedy, the found-object mascot of The WB, has studied the hip-hop moves and inflections almost too well. His down-in-the-hood shtick, which draws from both Eminem's sulky slither and Snoop Dogg's stoner drawl (''Tell me somethin' I dowwwn know!'' snarls B-Rad), is set up to be a parody, but it turns into more of a straight imitation, a kind of walking audition for ''American Rap Idol.'' He wears out his welcome in five minutes.
''Malibu's Most Wanted'' tries to build a farce out of our poseur culture. To get B-Rad off the radar, O'Neal hires two actors to impersonate real gangstas and scare his son straight. It sounds promising, but Taye Diggs and Anthony Anderson do fake hardcore menace as if they were playing a generic cliché of thugs from South Central. ''Malibu's Most Wanted'' is a send-up of rap personality in which no one actually has a personality. The joke, alas, is on the movie.