Jason Sudeikis guest stars as an old member of the gang, Schmitty, who the kinds try to bring back in.
Added:

It's Always Sunny in Philadelphia Season 6 Episode 8 Quotes

Principal: I'm a little confused, are you telling me this photo of Bruce Jenner is your resume?
Charlie: Well, when I showed up this morning I didn't have a formal resume on me so i was sort of hoping the photograph of Mr. Jenner could represent the standard of excellence I'm hoping to bring to his position.
Principal: And you're looking for a job as a substitute teacher?
Charlie: Substitute janitor.

Dee: So I shouldn't give up on my dream?
Teacher: You must give up on your dream, it's far too late for you.