Rock Hudson is the clone of the famous actor, Rock Hudson. He's served very little significance, in the show, but has made scattered minor appearances.
He appeared in the background in "Episode Two: Election Blu-Galoo", as a crowd member, running to the closed circuit TV.
He didn't appear, but was mentioned in "Makeover Makeover Makeover: the Makeover Episode" and "Changes: The Big Prom: the Sex Romp: the Season Finale", as Marie Curie's boyfriend, despite him being gay. He soon left her for Oscar Wilde.