Yeah how the hell they ended up together is a mystery to me, they make a really weird couple. The extreme height difference is the least weird part.
I mean, James is extremely polite and orderly. He's patient, he thinks things through, he's well respected, a good leader. Just, A+ horrifying gentleman rabbit demon.
Meanwhile Dexter is an erratic, hyperactive tornado of a person with zero self-restraint or manners. Obnoxiously flirty and all up in people's personal space. And while he seems to do a lot of it on purpose just to mess with people, he must be really tiresome to be around.
It defies all logic that they would even get along, but I guess Dexter is less awful when alone with people he actually cares about.