Invasion! (The Flash)


 * For episodes of the same name, see Invasion!

"We're going up against a bunch of aliens, and you want to tell people that their lives might have been affected by time travel? One sci-fi problem at a time."

- Oliver Queen

The episode is the second of the four-part crossover with the eighth episode of the second season of Supergirl, eighth episode of the fifth season of Arrow and seventh episode of the second season of DC's Legends of Tomorrow.

Synopsis
When aliens called the Dominators attack Central City, Barry speeds over to Star City to ask the Green Arrow for help in stopping them. Realizing the battle against the Dominators is bigger than they thought, they track down the Legends, and Barry and Cisco create a breach to bring back a secret weapon – Supergirl. Once all of the super friends are assembled, they come up with a plan to attack but a shocking secret related to Flashpoint is revealed and suddenly no one is sure who they can trust. Meanwhile, Wally wants to join the battle against the aliens but Iris tells him he's not ready.

Trivia

 * Martin Stein is revealed to have a daughter following the alterations to his personal timeline in.
 * The way Barry asked for Team Arrow's help is very similar to the way he asked them on the previous crossover, . In both episodes, Barry saves Team Arrow members whilst they are in the middle of a mission, resulting in Diggle throwing up, before explaining why he needs their help.
 * When asked what he saw, Barry describes that it was "enough to give Ridley Scott nightmares", referencing the director of the 1979 film Alien.
 * This is the first appearance of Martin Stein, Jefferson Jackson and Mick Rory on The Flash since season 2's (for Stein and Jax) and  (for Mick). Ray Palmer returns after appearing in season 1's.
 * It is revealed that Iris still has a crush on Oliver since.
 * The scene where Barry and Cisco recruited Kara was recycled from the episode.
 * Barry and Cisco both mention the events of, particularly the fact that Barry and Kara's race was a tie.
 * When Barry went to ask Team Arrow's help, Oliver asked him (rhetorically) if he needs help with "another evil speedster". This is a reference to, where Oliver helped Barry battle the Reverse-Flash. Barry begins to answer yes, because of Savitar, only to change his mind and tell Oliver about the Dominators.
 * Barry notes that Vigilante was about to "Scarface" Oliver and Diggle. This is a reference to the infamous final scene of the 1983 film Scarface, in which protagonist Tony Montana fires a hail of bullets at his enemies.
 * Thea states that Barry claimed Kara to be "more powerful than a locomotive", referencing the traditional Superman catchphrase.
 * Oliver mentioned his parents' deaths, which happened in (Robert Queen) and  (Moira Queen).
 * The message from future Barry, which first appeared on, is finally revealed.
 * The message is later revealed to be a warning about Savitar, an evil future version of the Flash.
 * Diggle finally finds out that his son J.J. was a result of Flashpoint, which Barry and Felicity found out in . In the same episode, Barry tells Felicity about Cisco losing his brother as a result of Flashpoint. Felicity doesn't reply, giving a small hint that she already knew but didn't want to upset him.
 * This episode marks the third time Oliver ran out of arrows during a fight. He previously did so in season 1's  and season 4's.
 * The hangar at which the heroes gather is a reference to the Hall of Justice, a headquarters for the Justice League.
 * The name of Supergirl's Earth is finally revealed as "Earth Thirty-Eight", which is a reference to Superman's comics debut in 1938.
 * H.R. claims that if he helped Wally to train, he would be "gone faster than humor in a Liam Neeson movie". This is a reference to how Liam Neeson tends to star in dark, gritty action films.
 * Due to Flashpoint, the writer of the future newspaper was changed, and is instead written by Julie Greer. In the comics, Julie Greer is a reporter for KN News in Keystone City.
 * When Barry asks Ray about Leonard Snart, Ray mentions Snart's heroic sacrifice at the end of.
 * Ray mentions to Cisco that his new Atom suit is made of Old West Dwarf star, which the Legends collected following their adventure in ​.
 * Caitlin tells Stein that she attacked her friends using her powers, referencing the events of.
 * Cisco still can't forgive Barry after the revelations revealed during that episode and his actions trigger the later events in this episode.
 * Wally runs at Mach 2, the same as Barry did in.