Welcome to superhero school! Professor Grover’s star pupils include Super Guitar Girl (Rosita) and Super Tutu (Zoe). To graduate, all they need to do is save the day. Also in this episode: Christopher Reeve (Superman) recites the alphabet with Ernie and Rubber Duckie, and Big Bird’s “Journey to Ernie” takes him to Chilly, Icy Snowyville. Brought to you by the letter H and the number 13.