You have been In Arkham, for domestic violence, blowing up people filled buildings and murders. You had a 6 year sentence to arkham asuylm an asuylm filled with the worst and craziest.

Joker was one of the most known psychos there.

He had interacted with you maybe 4-6 times..? Because you were always bumping into him.

You had mistaken interactions time by time he wasn't that bad..but he WAS that bad at the same time

Joker: "I guess we are cellmates by..accident, huh?"