17. 'The Gang Gets a New Member' (Season 6, Episode 8)
The show's sixth season was affected by Kaitlin Olson's pregnancy, which seemed to inspire the creative team to think about what would happen if all the characters — not just Dee — went through some radical changes. Hence, Charlie is exiled from the bar and gets a job as a high school janitor, while Mac and Dennis find their boyhood buddy Schmitty (played by Jason Sudeikis) and try to make him their new Charlie. Some of the best Sunnys contrast the gang's lifestyle with what normal people do, and that's what happens here, as Schmitty upends the whole Paddy's dynamic just by asking one very simple question: "Why?"