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:
- "Medusa" (Supergirl)
- "Invasion!" (The Flash)
- "Invasion!" (Arrow)
- "Invasion!" (DC's Legends of Tomorrow)
- The crossover was marketed as Heroes v Aliens.
- There are eight characters who appear throughout the entire "Invasion!" crossover (not counting "Medusa," which takes place entirely on Earth Thirty-Eight and only sets up the story at the end of the episode). The characters are Oliver Queen/Green Arrow, Barry Allen/The Flash, Kara Danvers/Supergirl, Ray Palmer/The Atom, Sara Lance/White Canary, John Diggle/Spartan, Felicity Smoak/Overwatch and Cisco Ramon/Vibe. The only characters who appear in all the "Invasion!" episodes and "Medusa" are Barry, Kara, and Cisco.
- Notably, all eight of these characters are featured in the posters highlighting the event (shown below).