Invasion!

Invasion! is the name of the 4 part crossover event between Supergirl, The Flash, Arrow and DC's Legends of Tomorrow. The crossover aired over four nights from November 28th to December 1st, 2016. The episodes that were involved in the crossover were:
 * (Supergirl)
 * (The Flash)
 * (Arrow)
 * (DC's Legends of Tomorrow)

Trivia

 * The crossover was marketed as Heroes v Aliens.
 * This is the first crossover between another shows exept Flash and Arrow.
 * This is the first crossover in which most of the parts share the same name (Invasion!)