Joker 2.0 is a cyber version of the Joker made by a mishap with a machine the Clown Prince of Crime was using to mentally download money. Before Batman could trap Joker 2.0 inside the machine, Marty, the Joker's nerdy new henchman, downloaded him, allowing him to go wild.
Marty informed Joker 2.0 that Wayne Enterprises had created special nanobots that could self-multiply and take on any shape. Joker 2.0 was hacked into the system and used the nanobots to build a new body.
After escaping from the hospital (which he'd been sent to following the accident), the Joker returned to his hideout and met Joker 2.0. The Joker's henchmen couldn't choose which one to follow, with both Jokers deciding to become partners. Unbeknownst to both of them, each planned to double-cross the other. Later, they both went on a crime spree in Gotham City, making it harder for Batman and Robin to stop them. Joker 2.0 eventually decided to take over Gotham and get rid of Batman, Robin, and the original Joker in one fell swoop, eventually growing into a giant body.
Robin, finding out that Marty was the Captain Slash character in an online game, came up with an idea. Robin told Batman that Joker 2.0 could be trapped inside the game. Batman, in the Bat-Bot, sent a signal from Joker 2.0 into the computer, causing the Nano-Joker to be trapped inside the game forever.
Joker 2.0 was later seeing being beaten up by Nightwing, Robin's character in the game.