At the end of the last run on Batgirl, the creators sneaked past an interesting thing.
The idea that the events of the comic book The Killing Joke by Alan Moore and Brian Bolland, never intended as an in-continuity comic, but controversially treated as canon by the rest of the comics – had never actually happened. Were but memory implants. And, while Barbara Gordon was still incapacitated physically, it wasn't at the hand of The Joker, in an attempt to drive her father mad.
Well in the upcoming Batgirl & The Birds Of Prey out this week… it does suggest that the events of The Killing Joke did, actually happen.