Benjamin is a friend and former college roommate of Schmidt's.
Benjamin is considered to be somewhat of a 'douchebag' to the roommates, however Schmidt seems to look up to him. He is very self-centered, and believes he is God's gift to women. This is apparent when he hits on Jess, expecting her to be flattered after being so forward. When she doesn't reciprocate, he refuses to back down, resulting in an altercation between him and Julia (she punches him in the face). It is also shown that he and Schmidt have a love/hate friendship - in their college days he used to make Schmidt sing "We Built this Schmidty (on Tootsie Rolls)" because he was fat.
When Schmidt sees him again in season 5, he’s engaged; his fiancée is just as shallow as he is