When asked to think of an evil comic book character, there's a 99.9% chance that the Joker is the first character to pop into your head. With so many of DC's most depraved comic moments being the work of the Clown Prince of Crime, it's inevitable that he'd become synonymous with doing bad things, as when you see him in a comic there's a strong chance that's exactly what he's up to.
But having Joker only do evil deeds would really make for a dull character. One of the most exciting things about the Clown Prince is that he's unpredictable, and that you're as likely to get a weird knock-knock joke and a pat on the back from him as you are for him to remove your frontal cortex.
True to form, this means that sometimes the clown does genuinely heroic things - such as the fact that he's actually been responsible for saving the world at least three times now.
They're not always done for the right reasons, but even with this in mind there's still a shocking number of occasions in which Joker was arguably the hero of the story - whether we like to admit it or not.
10. Turning On The Black Glove
Villain team-ups are unpredictable at the best of times, as you've always the chance that these unpredictable bastions of evil will turn on each other instead of the superhero they are supposed to be opposing, totally undermining the entire purpose of teaming up.
With a villain as unpredictable as the Joker, too, the chances of this happening skyrocket. This would serve to explain why the Laughing Prince decides to suddenly break his ties with the Black Glove, sabotaging their plans by allowing Batman to override the security locks on Arkham Asylum, trapping the members of the Glove inside.
The villainous dinner party does technically provoke Joker into this - by refusing to let him bet with the rest of the organisation - but there's also a strong implication that The Pale Man has been setting up his nemesis to beat the villains all along. How so? He avoids initially fighting Batman because his 'nails are still drying', which is up there with 'I'm walking my goldfish' in terms of weak excuses.