Finally we have a chance to assess America's most famous aspiring actor in his work off the witness stand. In the newest episode of The Watcher (Tues., April 11,9 p.m. ET), Brian "Kato" Kaelin plays a cruel businessman, who, murdered by his wife's lover, is reincarnated. We still see Kato; everyone in the story sees a black dishwasher. (After this episode, The Watcher, a feverish but often entertaining anthology series on UPN, goes on hiatus.) Kaelin does well as the imperious executive, his hair pulled back severely in a ponytail. But in the afterlife segment, he's clearly in over his head. Of course, Kaelin's best role is as the hang-loose houseguest who is a welcome adornment to any Jacuzzi. Who can forget when Marcia Clark snidely asked him if O J. was "thrilled" to have his company on a McDonald's run last June, and Kato shot back, "Wouldn't you be?" But Kato came along too late for his ideal role: permanent guest on Hollywood Squares. Can't you almost hear it? "I'll take Kato to block, please, Peter."