Real Name: Tim Drake
First appearance: "Batman Beyond: Return of The Joker"Creator: Bruce Timm
The Birth of Joker Jr One Night, Robin was patrolling the nights when he heard cries for help. He followed the noise until he found two muggers mugging a woman. He came to the help of the woman and scared the muggers off. However it turned out that the Lady that Robin had helped was no-other than Harley Quinn. She hit Robin With a Mallet and took Tim Drake to the rundown Arkham Asylum where The Joker and Harley Quinn where planning to start a 'family'.
The Joker started torturing Robin for secrets and Robin tried his best, but the pain was too unbearing that soon after, he gave up. He told The Joker who Batman really was, where the Batcave was hidden and that was when "The Joker Jr." was born.
The "Birth" of Joker Jr
Batman and Batgirl noticed that Robin was missing and started searching for him everywhere. They asked every underworld connection they knew but none of them were aware where Tim Drake was. Finally after three agonising weeks they went to the rundown Arkham Asylum. They checked a couple of rooms and they noticed that someone was singing 'hush little baby' in the operating room. They went inside the operating room to find Harley Quinn setting the table and The Joker reading the newspaper in a 1950s sitcom-style house. After the Joker told Batman of what he did to Robin, Joker trapped Batman and showed him what he did to Robin. Batgirl threw Batman a knife and Batman escaped the ribbon. When Joker told Joker Jr to say hello, Joker Jr broke into Manical laughter. A fight broke out with Batgirl chasing after Harley Quinn and Batman after The Joker. Harley Quinn told Joker Jr to 'get mommy's Bazooka' and Batgirl was attacked by a number of rockets whick she swiftly doged. Batgirl and Harley Quinn fought over a cliff and Batgirld slipped Harley Quinn's hand and Harley Quinn supposedly fell to her death. The Joker passed Joker Jr a Flag gun and told him to kill Batman once and for all. Joker Jr then was about to kill Batman and then aimed at The Joker and shot him. Joker's last words were "That's not funny. Not at all."
Joker Jr then breaked into Manical laughter once more and that slowly turned into tears and crying. Batgirl came to Tim Drake's side comforting him saying "It's okay, we're here now"
Returning to normal After that incident, Bruce told Tim that he forbade him to be robin again and then he continued on his life normally once more, becoming married, a couple of kids and becoming a top notch communications engineer. However, a device with a program similar to The Joker's mind in it had, unknown to Batman or Tim Drake, had been placed on the boy's neck on that fateful night.
"Batman Beyond: Return of The Joker" this device transformed the elderly Tim Drake into the Joker in Jekyll and Hyde-esque manner. The more Tim became The Joker, the closer the program came to becoming in control completely.