Real Name: Tim Drake
First appearance: "Batman Beyond: Return of The Joker"Creator: Bruce Timm
The Birth of Joker Jr One night, Robin was out patrolling the city when he heard a cry for help. He followed the noise until he found two muggers trying to rob 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 him to the rundown Arkham Asylum where The Joker and Harley were planning to start a 'family'.
The Joker started torturing Robin for secrets and Robin tried his best, but the pain was too unbearable that soon after, he gave up. He told The Joker who Batman really was, where the Batcave was hidden and that was when "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 of where Tim Drake was. Finally, after three agonizing weeks, they went to the abandoned 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, he trapped Batman and showed him what he did to Robin. Batgirl threw Batman a knife and he escaped the ribbon. When Joker told Joker Jr to say hello, Joker Jr broke into maniacal laughter. A fight broke out with Batgirl chasing after Harley Quinn and Batman after The Joker. Harley told Joker Jr to 'get mommy's Bazooka' and Batgirl was attacked by a number of rockets which she swiftly dodged. Batgirl and Harley Quinn fought over a cliff and Batgirl lost hold of Harley's hand and she supposedly fell to her death. The Joker passed Joker Jr a flag gun and told him to kill Batman once and for all. He then was about to kill Batman, but aimed at The Joker and shot him. Joker's last words were "That's not funny. That's not..."
Joker Jr then broke into maniacal laughter once more and that slowly turned into tears and crying. Batgirl came to Tim's side, comforting him and saying "It's okay, Tim. It's okay."
Returning to normal after that incident, Bruce told Tim that he forbade him to ever be Robin again, blaming himself for what happened and swore he'd never endanger another young partner. Tim soon left, determined to make it on his own. Years later, he continued on his life normally once more, getting 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, Barbara, or Tim Drake, had been placed in 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.