"I don't know if it'll cheer you up or not, Napier, but I know who Batman is."
Joker looked up at The Riddler, who was crouched in front of him. "... You do?"
Riddler nodded and opened his mouth to spill the beans.
"Don't tell me."
"Hm?"
"Where's the fun in that? I don't wanna know who Bats is."
"Are you sure you're not just worried that if you find out his name, you'll kill everyone he loves?"
Joker let out a small laugh, if it could even be called that. "I'd have to kill myself then, wouldn't I? Let's just keep it undisclosed."
"Well... Who do you think he is?"
Joker shrugged. "I don't really care. Batman is Batman. Whoever he is under that goofy mask isn't."
Riddler furrowed his brow a bit at Joker's surprisingly-sane reasoning. He supposed it had to do with the mellowing effect Joker's past had on his behavior, and that the next time the clown slept, it'd wear off and he'd come running back to Riddler for the answer to the biggest riddle either of them had ever come to know.
"What's that face for, Nigma?"
"Nothing. I just like this side of you, that's all."
"What, the side that doesn't like to laugh? That's a rare one. You should feel special." Though it was a joke, Joker mumbled this in monotone.
"I do."
Joker, with his makeup smeared on his face, drowsily looked up at Riddler. "You do?"
"With you? Always."
Batman kicked open the door to an apartment that Mad Hatter had apparently been seen entering. Thus, it wasn't seeing Mad Hatter inside that surprised Batman - it was the state he was in.
Hatter was gagged and beaten, and he was tied down to the bed in the corner of the room. Batman walked over and tore off the gag.
Hatter snarled at him, "He stole my Alice."
"Who took Joker?" Batman demanded the answer.
"The Cheshire Cat."
"Was it The Riddler?"
"Yes."
Batman turned to storm out.
"Hey, wait! Aren't you going to untie me?"
"You'll find a way." That said, Batman flew out of the apartment. He'd have to find Riddler now, it seemed. He was frustrated by that development, but was fine to go through the riddles, when suddenly...
"Incoming call from The Joker." His portable Batcomputer within his suit announced that Joker was calling him. Quickly, he tapped into it, and was almost compelled to speak, but held it back.
That was when the music started to play in the background of the call.
"I know~...
"someone who wants you~...
"Guess who~, gue~ss who...
"He wonders, Bats, if you want him too~?
"Do you~?
"He'd love to hold you in his arms,
"and whisper in your~ ear~,
"and tell you just,
"how grand you are,
"and ju~st how much he ca~res.
"I know~...
"someone who loves you~...
"Guess who~, gue~ss who...
"A~and loves those little sweet things,
"you sa~y,
"and do~...
"I try to tell you in my song;
"can't you play a~long?
"The one who loves you, Ba~atman...
"... is me..."
Batman stood still, confused and stunned by Joker's singing, yet at the same time, not exactly surprised.
"Isn't it nice of Riddler to let me get in touch with you like this? Maybe I should be singing this to him. What do you say, ... Bruce?" Just like that, the call cut to silence. Joker had hung up.
Batman was shaken to the core by that one, last word - his name.
Joker knew his name now.
It wasn't particularly the knowledge that Joker knew his real name that scared him so bad; it was the concern of what he'd use it for.