Corrected entry: Right after the Joker falls from the cathedral the shot slowly zooms to him lying dead on the ground below, with the laugh box giggling away. Watch his left eye closely and you can see it blink, despite his being "dead". (00:01:55)
Mad Ade
20th May 2006
Correction: Involuntary twitches are common in the recently dead, especially if the death was caused suddenly. The blinking eye could have been nothing more than a final twitch as the brain shuts down. For a cinematic reference, look at The Rock, when a body is twitching after being killed, freaking out Nic Cage. It's not often portrayed, but does happen.
Mad Ade