Stumble is pulling out one more surprise with Katey Sagal joining the show in a key role. Us Weekly can exclusively confirm that Sagal, 72, appears in the season finale, which airs Friday, March 13. Sagal portrays Marg Hargberg a.k.a Courteney's (Jenn Lyon) former coach who influenced the way she has taught cheerleading. In Us' exclusive clip from Friday's episode, Courteney accidentally runs into Marg at College Nationals. "I just can't believe my old coach is here. Marg would just really scream at me and say very mean things about my legs. She gave me PTSD," Courteney says.