When:Season 2, Episode 2 Storyline: Will (Matthew Morrison) feels insecure when he discovers Emma (Jayma Mays) has a new boyfriend, Dr. Carl Howell (John Stamos). Secretly wanting to catch a glimpse of Emma's new beau, Will convinces her to bring in her dreamy dentist boyfriend to talk to the Glee Club about dental hygiene. Why It's Great: Whether he's playing Uncle Jesse on Full House or a nerdy dentist, John Stamos is a stud! Stamos' character turned into a recurring role as he eventually marries Emma, then seperates because she refuses to give up her virginity. The break-up was for the best -- after all, "Everyone wants to see Emma and Will together," Stamos told Access Hollywood. This complicated love triangle was nice while it lasted!