He probably could have gone years without ever finding out about it. Normally Joker went out of his way to point out the "similarities" between them. But he had never mentioned the tattoo. He probably would have kept it from him for as long as he lived, Joker being Joker.
He'd only found out due to a particularly large gash the batarang had caused, tearing through the purple vest and button down shirt, exposing a compact bleached white chest. And even after that injury, he hadn't noticed. Until he'd pinned Joker beneath him to the concrete floor. He'd taken one moment to look over Joker and assess the situation.
That's when he noticed the tattoo. It was small. At first glance it was just a black smudge on the left side of Joker's chest, over his non existent heart. It wasn't even overdone. There wasn't a joker "flair" to it. Just the one mark on his chest. A bat. A single bat, that resembled the insignia on his suit. There was no writing on it, no HA! HA! HA! Printed madly around it. Just a bat.
Joker caught him looking and smirked, ruby red lips pulling up in something other than amusement. "You like? Fitting isn't it." he paused as though waiting for his "Batsy" to reply, but got nothing. "A piece of you will always be with me." Joker let out a cackle. "Y'see, you belong to me, and I to you. This." A long slim finger tapped the tattoo fondly as he liked his lips. "Is just a reminder of that."
He wished he hadn't seen the tattoo. He wished he could just let Joker die with that one "similarity" because...he didn't want to admit to having a fancy J, small enough to be missed, printed over his own breast.
isn't that something Joker would do? Getting a bat over his heart. Hee. Review please!