4) Aquaman
Ok, now we’re getting onto the big boys. A few members of the Justice League are mulling around the Arrowverse, but several easter eggs suggest that the main hitters of the team are also out there somewhere.
One such example is Aquaman. He definitely exists on Earth-2, as Hunter Zolomon (pretending to be Jay Garrick) said that one of his best friends was from Atlantis – which is of course Aquaman’s kingdom.
A deleted scene from The Flash’s pilot episode would have suggested that Aquaman was on Earth-1, as well. In it, Joe moaned at Barry for skipping work to go to Amnesty Bay to investigate claims that there was a man there “who could talk to fish.” This could be considered non-canon because it was deleted, but we’re counting it here, as we really, really want this to be the case.