1. Johnny Trouble is a nick-name for a person who tends to get you or an entire group of people in trouble when you go out but usually does it in such a way that is fun for everyone and so people let him continue to hang around.
2. If one is out looking for Johnny Trouble, one is not being one-self and is out looking for trouble, or alternatively, a good time that may or may not lead to trouble.
"Yeah, Johnny Trouble met us at the club and after the 4th shot, they asked if we could move the party elsewhere so we did."
"I'm gonna go see if Johnny Trouble's out and head over to that shady club on the bad side of town."