cosima/tali.
He's kind of got a tragic backstory thing. You'll probably hear him talking about "the other guy." He used to work for the military and was trying to recreate the serum that made Captain America Captain America. It backfired on him and now whenever his heart goes above a certain rate, he turns into a raging, green anger monster called the Hulk. He's spent his life running from scientists who want to study him.