I loved all the old JLA/JSA Earth-1/Earth-2 team-ups. One thing I loved was this particular story in #37. It seems Johnny Thunder, who was basically a 1940′s version of Snapper Carr with a pet genie, got in a snit over not having an Earth-1 counterpart in the League (because no-one made the obvious parallel I just did). Johnny goes to Earth-1 to see his alternate self, who turns out to be a criminal, and insanely capable. Basically, Earth-1 is to Johnny Thunder what Earth-3 (home of the CSA) is to the League.
Evil Johnny gets control of the Thunderbolt and begins a reign of terror. He also finds a great way to get the league out of the picture:

I get how the swap with the Flash works, and I guess the guy could have stolen Ray Plamer’s belt and another GL’s ring, but how the hecks do you “swap” criminals in place of Superman and J’onn?