“Schmigadoon!,” a parody of iconic musicals, stars Cecily Strong and Keegan-Michael Key as a couple on a backpacking trip designed to reinvigorate their relationship when they discover a magical town in which everyone acts as if they’re in a musical from the 1940s. They then discover that they can’t leave until they find “true love.” The first season of the six-episode series also stars Alan Cumming, Kristin Chenoweth, Aaron Tveit, Dove Cameron, Ariana DeBose, Fred Armisen, Jaime Camil, Jane Krakowski and Ann Harada.