Did you never play Fallout 3? It's a post-apocalyptic world full of wonderful, hilarious moments. Skyrim is the home of the Nords, who are the drunken jokers of the ES world. Besides, Bethesda loves adding humor to their games. There will be humor. PERIOD.
Personally, I'm not a huge fan of this recent trend of games moving in an increasingly dark direction. Take, for example, Mass Effect when compared to Mass Effect 2, or Dragon Age: Origins to Dragon Age 2. In both cases I liked the former better than the sequel, and I don't want to find myself disliking Skyrim for the same reason.
This isn't BioWare, dude. This is Bethesda. Don't worry (also, don't compare the two. EVER.).