Who'd have thought that after acing their foray into reality TV, Jessica Simpson and Nick Lachey would lay such a rotten egg with the good old-fashioned Nick & Jessica Variety Hour? After all, they're supposed to be entertainers, right? But the only entertainment here is of the unintentional kind. Jessica's facial contortions while overemoting on her duet with Jewel? Funny as a fun-house mirror. Nick's harmonizing with K.I.T.T. the car from Knight Rider? Arrestingly idiotic. Nick and Jess making like Sonny and Cher for the closing, dueling-belters number ''I Got You Babe''? Pure, campy kitsch. All this plus guest appearances by Mr. T and Johnny Bench! Do-ya-love-it? EXTRAS None, and that's a shame: A behind-the-scenes look at the making of this train wreck might have been perversely irresistible. You know, like a bad reality show.