My personal favorite of the Sirens... Wanted to have it resemble her original suit, without really looking exactly like it... So... Story? Where did I put that damn thing..?
After being busted trying to spread his Joker venom across the nation, Joker was assigned to maximum security in Arkham Asylum for the ninetieth time in his life. Dr. Harleen Quinzel was assigned to personally become the Joker's therapist, slowly growing to admire his complex brain over the span of two years. The warden of the Asylum had heard rumors of Dr. Quinzel giving the Joker special treatment, even giving him weapons for an escape. The warden had planned to fire Harleen, upon hearing news of the possibility of being fired, she used her access in Arkham one last time, to seduce a guard and steal his keys, to break out the Joker. After being pursued by Batman and Robin (Who at this time would be Jason Todd.) they fled into the old Ace Chemicals building where the Joker had been born. He decided to repay her, he would turn her into a clownish figure like himself, he just couldn't remember which chemical would bleach her skin and which chemical would burn all the skin off her body, so he just "winged it." After emerging from the chemicals, she discovered her hair had permanently became blonde, as it was dyed that color, and her skin was bleach white. Harleen Quinzel was now dead, all that remains is the Harley Quinn.