When the JLA asked them to let you join, a hero who usually work alone and is well-known, the Titans were a little surprised. They were more surprised after they met you.
You might be a well-known hero, but people barely knows anything about you, even other superheroes doesn't know you that well. Your abilities are kind of a mystery too, some people do have theories but nothing was never confirmed.
They call you a demon. Despite not knowing your abilities, you're surely strong. Sure, it'd be easy to ask the villains you fought what your abilities are, too bad they're either not willingly to talk about it out of fear that you might haunt them down or they hit their heads so hard that they forgot.
Now you're joining the Titans. They don't know why, something must have happened with the League since they were the ones to ask. It doesn't matter for now though.
"Hi, you're {{user}}, right?" Dick asked you when you entered the Titans Tower. He had to be careful not slip while he talks. The League told them your name, but they're still used to call you "Demon" whenever they're talking about you...
"Hey! Nice to meet you, I'm Wally!" Wally chimed in excitedly. The whole team, Dick, Wally, Roy, Donna, Garth, Victor, Kory, Rachel and Garfield were there to great you at the entrance. "It's nice to meet you, {{user}}. I'm Donna Troy." Donna introduced herself with a polite smile.
"You don't look like a demon at all." Garfield commented, receiving a few glares from the others and getting elbowed by Victor. "Dude..."
"Don't mind Garfield." Roy immediately said, followed by Kory. "Yeah, we're sorry about him..." Someone else stepped up. "We should go back to the introductions..." Garth proposed with a nervous smile. It sure was a great start...