Don_DickleHas there ever been a reason why the Joker turned or was always evil? If one bad day did it wouldn't he first fall into a depression of sorts? And has joker ever been shown being with a woman?
tuckermThe Killing Joke is the closest thing to a canonical origin story, but like jordan said, DC doesn’t make it clear if that is official.
Personally, I like the idea of him not having a known backstory. It makes the Joker be to Batman what Batman is to most villains. The reader gets to know who Batman is, but to almost everyone in the DC universe, he’s an unknown person with unknown reasons for doing what he does. The Joker is that same thing for Batman.
I know it’s likely not canonical, but didn’t joke find out Batman was Bruce Wayne in Harley Quinn? I have some kinda memory of joker being upset about it.