I found this picture on Hentai Foundry and I knew it would be great for a game.
Essentially, I have two ideas that this would work with. I want to play Batwoman in either one.
1.) Harley decides she is going to give Mister J a gift. Finding Batwoman, she uses a new version of laughing gas which has been treated with a version of Scarecrow's fear gas. This version gives the victim the typical grin but also sends them toppling over into insanity. Batwoman is hit by a dose of this gas and at Harley's prompting, is driven crazy. Soon Mistah J will have a pet bat..a giggling, drooling, nymphomaniac Bat.
2.) Batwoman and another superheroine are hit with a large dose of this laughing gas. Both of them go insane and proceed to do horrible perverted and nasty things to the other. The laughing gas has removed all sense of morality and decency. All they care about is getting at the other. All while Harley and the Joker sit back and watch the once proud heroines fucking.