Either or, characters or real people. I think their characters are based on very dumb/funny versions of themselves. When I've seen them on documantaries or in commentary like on Eagle vs. Shark, they do strike me as INFP and INTP. They seem very go with the flow.
I agree, it can be funnier after watching it. Each time I watch it though I appreciate something different. And reoccuring things - like the camera phone making an apperance from time to time is cool