Ashton Kutcher pulled the plug on ''Punk'd'' last month, but he'll soon be back on MTV playing hidden-camera practical jokes on hapless saps. According to the Hollywood Reporter, he's planning a new series called ''My New Best Friend.'' Based on a British TV show of the same name, the series will have a premise that sounds awfully similar to Fox's upcoming ''My Big Fat Obnoxious Fiance.'' In Kutcher's show, for which MTV has yet to set an airdate, a contestant can win cash by trying to fool friends and family by passing off a complete stranger -- an improv actor hired by the show and directed to behave boorishly -- as his or her new best bud. (At least the contestant doesn't have to take the deception all the way to the altar, as on Fox.) Kutcher, who announced last month that he was yanking ''Punk'd'' before it had the chance to get tired, will produce ''Best Friend'' but not appear on camera. Guess that means we won't be seeing the episode where he fools the world by trying to pass off a celebrated middle-aged actress as his new girlfriend.