Sayonara Zetsubou Sensei, Detroit Metal City Recommendations
Both are comedies with random humor that make fun of social groups and their values. Detroit Metal City has a more well-defined history, while Sayonara Zetsubou Sensei has more intelligent jokes and social analysis.
Both have dark humour. Detroit metal city is more focused on the dark side of comedy though. If you like dark humour, you'll enjoy both.