From TV Guide:
TVGuide.com: Is there anything about [Kevin] that is like you?
Baumgartner: I do have a childlike enthusiasm at times. I certainly enjoy life and get pleasure sometimes in childish things. Other people have said that I am the [cast member] most unlike my character. I take that as a compliment, though I do really love the Kev. Not that we should study the series in a “dramaturgical” way, but if you look at it, nobody doesn’t like Kevin. He is the guy who is friendly with everyone. He has a casual, friendly fantasy football game with Jim, they certainly get along. He totally tolerates Dwight. He doesn’t dislike anyone — except Angela.
Link: Brian Baumgartner Accounts for The Office’s Success