After both the Joker and an injured Batman were collected by Frankenstein, the loyal servant of Brother Eye proceeded to take them both to Arkham Asylum. There Frankenstein performed the surgery necessary to merge Bruce Wayne and the Joker together into one superhuman cyborg. Sharing one body, capable of rotating it's head, the Bat-Joker was then transported by Frankenstein to be showcased to Mr. Terrific. While the Joker side had almost instantaneously given in to the Joker's will, the Bruce Wayne side, horrified by what he had become, tried to hold out. Equipped with a Time Band, the Bat-Joker was sent back in time, arriving in front of Plastique.
Plastique was quickly saved by the Bat-Joker's target, Terry McGinnis, who was in turn saved by the Bruce Wayne of the past. The Bat-Joker, in order to preserve it's own existence, brutally beat Wayne, but did not kill him. Returning to it's task of hunting down McGinnis, the Bat-Joker found McGinnis confronting Tim Drake and was once again attacked by the Wayne of the past. The Bat-Joker proceeded to engage in a horrific battle against Bruce, Tim and Terry. Temporarily dismantled, the Bat-Joker easily recovered and began chasing after Terry. Eventually engaging in a one on one fight against Terry as the Brainiac God arrived, the Bat-Joker was defeated when one of Brainiac's spheres blasted it in the face. Much like the previous time, however, the Bat-Joker recovered and once again began it's march towareds Terry and quickly found him inside the Terrifitech Tower.
Continuing it's catastrophic march, the Jokerborg was in luck as Terry's armour had been weakened. Shooting Terry and filling him up with bullets, the Jokerborg reveled in it's victory and prepared to throw the fallen hero off of the Terrifitech Tower. However, Terry, with a final burst of heroism, took the Bat-Joker and destroyed it, letting gravity dispose of its remains.
Armed with great armor and gifted with an immense amount of superhuman strength, the Bat-Joker was stronger than most cyborgs of the End Future. Armed with futuristic weaponry, both energy based and ammunition based, it contained enough artillery to wipe out a small army. The entire Bat-Joker was powered by tubes that fed it nuclear energy, which, in case of a malfunction, the cyborg could use to transform itself into a nuclear bomb. On it's back, the Bat-Joker was armed with two giant iron claws to use to attack opponents from the rear. These claws gave the menacing impression of wings. Also armed with the cognition and navigation settings of Brother Eye, the precision of Bruce Wayne and the insanity of the Joker, the Bat-Joker was the ultimate weapon.