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Abruptly departed: Steve Carell
Played: "Office" boss Michael Scott
Lasted: 7 seasons (2005-11)
Why he left: Carell, who has starred in several feature films during his run on the NBC show, decided to solely focus on his film career, despite a slew of duds on his resume.
How it went down on air: Michael pursues his lady love, zany HR rep Holly, by leaving Scranton and moving to Colorado to be with her and her family. The staff of Dunder-Mifflin Sabre shed a tear for the "World's Best Boss" by singing their version of "Seasons of Love." Several comic legends, including Ricky Gervais, Will Ferrell, Jim Carrey and Will Arnett, attempted to fill the shoes of the regional manager, but they were all short-lived.