Great job with the voice, as well as the layering of the 'different' singers.
I was a little worried at the beginning, because that theme creeps me out, but I loved the waltz-like theme and the instrumental work.
With the "cape and his cave line" I started to hum the 'and his cat' but the meow and mancal took me by surprise. Also, I like how it drives the point that Batman can't kill Joker.
But, there were too many references to bats. I feel like the walking rodent population is under appreciated. Oh, and you don't change your style enough. [sub]To anyone who didn't read his latest column, this is a reference, made in jest[/sub]
Miracle, you just keep getting better.