Supergirl, Flash, & Arrow team up to fight Nazis and evil doppelgangers

The Flash wedding was supposed to be the crossover event of the season as most of the DC heroes showed up for the two-night, 4 episode event. The first two episodes aired Monday during Supergirl and Arrow, as "Crisis on Earth-X" parts one and two. But unfortunately some Nazis and evil doppelgangers crashed the party.