Dick Clark never gets old, but pop stars do. As EW has reported, the producers of NBC's new drama ''American Dreams'' are re-creating ''American Bandstand'' performances from the 1960s with young artists like Michelle Branch (Lesley Gore) and Nick Carter (Jay & the Americans' frontman). Recently, Usher taped an episode as Marvin Gaye. The R&B crooner, who calls himself Mr. Entertainment, hopes the role will lead to bigge things. ''People will get a chance to see my love for Marvin Gaye,'' Usher says. ''This opens the door for consideration for the role in a biography of his life.'' To prepare for the show, in which he sang Gaye's 1963 hit ''Can I Get a Witness,'' Usher listened to the soul man's earliest records and watched footage of concerts furnished by the network. ''They go very far to make it as authentic as can be,'' he says of ''Dreams''' team. ''I can be Marvin Gaye.''