Doomsday World Fallen

Watching The Flash behave so rashly, even looking as though he had seen a Speed Force tunnel for the first time. Peter guessed that this guy might have only just mastered the ability to open a Speed Force tunnel. "Could this guy have run into Supergirl's universe?" After briefly recalling it, Peter realized that the TV version of The Flash seemed to have first learned that the Speed Force could travel between universes—and discovered the existence of the multiverse—when he crossed into Supergirl's universe.