Superman and Green Lantern "merged" briefly, thanks to Apache Chief voice's power ring, in one of the Superfriends cartoons from the 70s. They had to combine their powers to do something they couldn't do individually -- escape a black hole or penetrate a force field -- something like that.
It was to escape from a black hole in the episodes "The World's Most Dangerous Game" but what does "Minnesota President" (inside gag) have to do with it?
On a side note Toyman has to be about the lamest character the LoD had. Dresses like a Batman villian though he is supposed to be a Superman villian, uses gimics best suited to the Adam West Batman, and two years later was killed off by the original Toyman.