I realize now that Robin was Nightwing before the end of the Animated series so this is what happened: Robin(TT) heard about Tim becoming Robin. Taking the name Starfire gave him (Nightwing) Robin sped off to Gotham City and then whatever happened there kept him from changing his name permanently. Before he left he gave Bruce the suit to hang up. Leaving the 3 members of the Bat-team; Bruce, Barbara Gordon, and Robin(Tim Drake). What happened to Robin(Tim Drake) can be seen last chapter or in Batman Beyond: Return of the Joker.
The Caped Crusader sat alone in the Bat-cave. Alfred had just gone upstairs to check on Tim Drake. Barbara had already gone home for the morning.
"How could you send them Bruce?!" Robin asked, appearing out of nowhere.
"Never thought I'd see you back here." Batman answered, turning around in the swivel chair.
"Never planned to be here. Why did you send the Justice League? I told you I'm not working with you anymore."
"You know as well as I do I had nothing to do with Green Lantern and Flash ending up in Jump City." Batman got up from his chair and silently moved closer to the leader of the Teen Titans.
"Then why were they there?" Robin demanded.
"Perhaps if you hadn't rushed to Gotham you could have asked them." The Dark Knight mocked his old partner. "Now I suggest you leave before you start a fight we both know you can't win."
"I've done the impossible before." Robin countered.
"When? When Starfire jumped into the future, inevitably changing history and keeping you from turning into Nightwing? Or when you and the other Titans fought Brushogun in Tokyo? You were the 1st partner I ever allowed. You were also the only one who ever understood the missions importance above all other concerns in the world."
"What's your point?" Robin demanded.
"But when it comes down to it none of you have the heart for the mission. Batgirl always fantasizing about the perfect relationship. Tim never truly understanding the seriousness of solemnity and apathy."
"And Jason?" Robin asked.
"He was barely a Robin." Batman glared down his ex-partner.
"The Bat-Glare doesn't work on me anymore Bruce. I've fought worse."
"No you really haven't."
"You mean going into the past and future to stop a time-traveling mortal. Hiding from Thanagarians and almost getting caught anyway? Or fighting yourself in a fight neither of you can win?" Robin asked. "What's worse than the Batman?"
Neither of them spoke for several moments.
"I think its time you found a new name." Bruce told the younger of the 2.
"What do you mean?" Robin asked.
"If Tim finds out that you're still Robin he won't accept that he can't be anymore."
"Why can't Tim be Robin?" Robin asked.
Batman turned around and sat back down at the master computer.
"If you won't tell me, I know who will." Robin left as silently as he had come.
Batman sighed.
Deep down the Dark Knight cared about each member of the team that had ever joined him. But Robin was the first. His parents were killed by a maniac, just like his own parents when he was 8 years old.
...
"You are, not a friend of Robin's?" Starfire asked GL and Flash.
"Never had the pleasure of meeting him until today." GL explained.
"I'm Cyborg." Cyborg said, extending his hand to the Green Lantern.
"Green Lantern, this is Flash."
"That's Starfire." Cyborg said, gesturing to Starfire, who was still unsure of whether or not to follow Robin.
"Why did Robin yell at you?" Starfire asked the 2 newcomers to Jump City.
"When your team first started Robin sent a message to Superman. Told him to not send anyone into Jump City. So he didn't." Green Lantern explained.
"But why does this make him hate you?" Starfire asked.
"He's a lot like Bats when you think about it. If we tried to go into Gotham Batman would just kick us out." Flash added.
"As in the Batman? The Dark Knight? The Caped Crusader? The Greatest Detective in the world?" Cyborg asked.
"Yeah, that's the one."
Starfire flew away as fast she could, she would not lose Robin.
"Starfire!" Cyborg called.
Raven and Beast Boy dropped out of the sky a second later.
"Nice of you to show up late." Cyborg joked.
"Where's Robin and Starfire?" BB asked.
"He took off that way. She took off after him I think." Cyborg said, pointing down the road.
"We have to get to him." Raven said.
"Why just him what about Star?" Cyborg asked.
"Because the Joker is about to catch him." Raven explained.
"The Joker?" Flash asked, for clarity.
"2 bit whack-job, cheap purple suit, green hair, and white skin." BB explained.
"But he..." GL began.
"Look I know what I saw, Robin was swinging from a building, he saw Harley Quinn in danger, he tried to help her, but she hit him with a hammer. Then the Joker showed up, kidnapped Robin, started doing weird experiments on him, then Batman and Batgirl show up, Robin kills Joker, and Harley Quinn disappears." Beast Boy said quickly.
"That's not possible." Green Lantern said.
"Why isn't it possible?" Cyborg asked.
"It is possible. I saw it through Azarath, there's no way I'd see a fake vision."
"Look girl, I don't know anything about your Azmuth..."
"Azarath." Raven said, glaring down GL.
"Azarath...sorry... But the Joker was killed last year." GL explained.
"Bats didn't give us the details but he told us the Joker wouldn't bother the Justice League anymore."
"Then why did Raven and I see Robin shoot the Joker? Robin's been with us for the past couple years." BB asked.
"Robin never told you he wasn't the only Robin?" GL asked.
"Another Robin?" Cyborg asked, "That's crazy."
"2 other Robins. One of whom just got taken off Batman's Bat-Team."
"And the other?" Raven asked.
"Gone." GL said sadly.
The 2 teams said nothing for a while.
"We still need to find Robin. This has to affect him in some way." Raven decided.
"Agreed. We're parked not so far away." Flash ran to the Javelin and powered it up.
"Where did he go?" Cyborg asked.
"To get us our ride." GL said.