Rhetorical Fanfic Question

If Roland Deschain steps through a door into Vincent Vega's head, and steps forward to take control of Vincent, is it still a pairing, or does it become a Roland/Jules, a Roland/Mia, a Roland/Lance, a Roland/Wolf pairing? Would I have to put Roland in Jules' head to make a Roland/Vincent pairing?

Basically, if two people become one person, is it still a pairing? And does that sound really naughty?