This episode was all about duets, and started with the Glee club, rather bizarrely, in a meeting for superheroes. My favourite of the rather eclectic bunch was Tina's guise as Asian Persuasian, naming her great power as Manipulation. Superheroes goes on to be a theme for the episode, as the singers don superhero attire in their performances.
As Coach Bieste explains, when you don a cape, you become another person, not dissimilar to the effect of what happens when performing on stage. To that end, then, it seems an apt motif for the Glee club to take on this week.