John Stamos has joined the cast of Glee as Will's new rival for Emma's heart. John is known for many roles on Broadway and I think will be an exciting addition to the cast.
In tonight's episode we learn that Emma has been dating her dentist, Mr. Stamos. John is rumored to appear next season as well, which could spell trouble for Will.
The hilarious part of the whole casting choice is that in the september 18th episode of Glee, Emma said this: "They say it takes certainty more than talent to make a star. I mean, look at John Stamos."