Galifianakis was interviewed by Marc Maron for his podcast (iTunes -- non iTunes) on the set of a movie (from facts in the interview, I presume it's Due Date). Galifianakis does fake-sincere very well, but I think he's real-sincere in this interview, at least much of the time when he's not outright joking.
Galifianakis grew up in North Carolina, part of the Jim Crow south, as a member of one of the many Greek families involved in the restaurant business. He relates this story, after saying that his father's side of the family is very dark skinned (this story starts about 30 minutes into the podcast):
My uncle Mike told me that in the fifties in the summer he would get really tanned -- dark eyes, dark skin. He sat on the front of the bus in Durham North Carolina. The bus driver stops and goes "Hey, boy. You have to sit in the back."Welcome to the South!
And my uncle goes "Why?"
He goes "'Cause you're negro, you have to sit in the back of the bus."
And my uncle goes "I'm not black."
And the bus driver goes "Well, what are you?" and my uncle goes, "I'm Greek."
And the bus driver says "You can't ride the bus"
Galifianakis, playing a petulant, narcissistic, dumb character (you know, like an entertainment "journalist") has done a series of celebrity interview web videos called Between Two Ferns. Worth a viewing.