That old guy with the cane is Bruce Wayne. Back in ‘99, they did a cartoon series called Batman Beyond. It was set in the future, about a decade or so after Bruce retires as Batman, after he was forced to almost shoot a criminal with a gun. Eventually, this kid named Terry McGinnis becomes the new Batman and Bruce trains him and acts like Oracle during missions. It’s an awesome as hell show. Anyway, JLU did an episode near the end of its run that crosses over into the Batman Beyond timeline and reveals something surprising: Terry is sort of Bruce’s son. Cadmus or Checkmate (forget which) created him using Bruce’s DNA as essentially a backup in the event Batman was killed.
Oh, and in Batman Beyond, there’s a massive gang in Gotham called the Jokerz, guess who they emulate? Speaking of Joker, Batman Beyond: Return of the Joker is a marvelous movie and needs to be watched. There’s a scene in that movie that will chill you to your core.
Edit: Forgot to mention Static Shock in the last gif. So, the writers managed to cross over three different shows in one episode. Nice.