Just the Ten of Us - Season 3 Episode 1 Betrayal
Overview: Wendy and Cindy go out on a double-date. But Cindy's date, Cort, is more interested in Wendy than the girl on his arm. Cort breaks a date to go to an Oingo Boingo concert with Cindy and takes Wendy instead. Marie realizes what's going on, so she coaxes Cindy into giving Wendy a taste of her own medicine by going out with Wendy's boyfriend, Blitz.