Xerko, a fellow famous Orkan idol of Mork's, appears in the Season 3 episode of Mork & Mindy titled "There's a New Mork in Town" (episode #13). The part of Xerxo is played in the episode by actor Lyle Waggoner.
Xerxo is a "young" (remember, Orkans age in reverse), middle-aged, but still handson looking, and famous Orkan who attempted to take Mork's job as the Watcher of Earth. Like Mork he also shows his emotions. But unlike Mork he is selfish and always does what ever he can to be at the top. Xerko, who's one of Mork's great Orkan idols, whose visit to earth puts Mork in hero worship mode. Only when Xerko shows great interest in replacing Mork so he can make inroads with Mindy does the full implication sink in.
Mork, who idolizes Xerxo, winds up regrettably "dueling" him with invisible swords, which he wins, as Xerxo gains one notable human emotion, humility, as he acquiecses in his attempt to woo Mindy.