Re: DC's New 52: Reviews and Discussion (Spoilers welcolme and likely)
I never got the impression that the Joker wanted to marry Batgirl. He was trying to torment her with her mother's severed ring finger. He was using the marriage bit as a joke, you know, because he's the Joker.
"In Brightest Day, in Blackest Night, no evil shall escape my sight. Let those who worship evil's might, beware my power: Green Lantern's light!"