This is a list of episodes which involve characters or plotlines from multiple shows in the Arrowverse. They are arranged chronologically, grouped by season.
Felicity Smoak visits Barry Allen in Central City to see his superpowers for herself, meets and helps Team Flash, and assists them in defeating Leonard Snart, aka Captain Cold.
Oliver Queen, Felicity Smoak and John Diggle head to Central City looking for the boomerang killer, and help Team Flash fight Roy Bivolo, a meta-human who can cause uncontrollable rage in others. Oliver and Barry's differing methods cause tension between the two, and they are forced to fight when Bivolo uses his powers on Barry.
Cisco Ramon uses Felicity Smoak's facial recognition software to look for meta-humans outside Central City and finds evidence of Mari McCabe using her animal powers against thugs in Detroit. He nicknames her "Vixen" and gives her whereabouts to Barry Allen, who decides to take backup; he and the Arrow show up at Mari's apartment. When Barry uses her name, she panics and runs away. Flash and the Arrow chase Mari, who uses various animal powers to evade them, including speed, wall-climbing, camouflage and flight. They eventually talk; Mari explains she was not in Central City for the particle accelerator explosion, a fact confirmed by Felicity Smoak, and refuses their offer of help, threatening them with violence if they return. Flash and the Arrow visit Mari again, offering to help train her if she intends to become a vigilante; she says she is, but wants to work things out on her own. She asks about getting a codename and Barry says they call her "Vixen"; he lets slip Cisco's name, giving her a clue as to his identity. (Takes place around the same time as "The Offer").)
Cisco Ramon helps Team Arrow and Ray Palmer defeat the meta-human Jake Simmons, aka "Deathbolt", who has come to Starling City thinking no-one can stop him with the Arrow gone. Simmons is imprisoned in the Pipeline, but Cisco and Ray realize he was in Opal City during the dark matter wave, making the source of his abilities a mystery.
Cisco Ramon and Joe West head to Starling City to investigate the real identity of Harrison Wells with the help of Quentin Lance. Cisco also meets Laurel Lance and upgrades her sonic device, renaming it the "Canary Cry".
Barry Allen decides to move the meta-humans from the Pipeline at S.T.A.R. Labs to the A.R.G.U.S. prison on Lian Yu, to protect them from the plans of the Reverse Flash. He enlists the help of Leonard Snart, but Snart double-crosses the Flash and frees most of the villains. Barry then fights the Reverse Flash, defeating him with the help of Oliver Queen and Firestorm.
In a flash-forward to six months in the future, Barry Allen visits Oliver Queen in a graveyard, apologising for missing a funeral. Oliver vows to kill "him", and asks Barry to leave before weeping over the grave.
In a flashback to his time infiltrating Baron Reiter's operation on Lian Yu, Oliver Queen meets John Constantine, saving his life while he is retrieving the Orb of Horus. In the present, Oliver calls in this favour from John to restore the soul of Sara Lance, who has been resurrected from the dead by the Lazarus Pit.
When Vandal Savage comes to Central City looking for Kendra Saunders, Team Flash ask Team Arrow to help keep her safe, but Carter Hall shows up claiming he and Kendra are reincarnated lovers. Savage follows them, and they learn from Malcolm Merlyn that Savage is an immortal looking for the Staff of Horus, and will stop at nothing until he finds it and kills both Carter and Kendra.
Team Arrow and Team Flash work together to save Kendra Saunders and Carter Hall from Vandal Savage, who is willing to destroy both Central and Star Cities in his quest to kill them. They enlist the help of Malcolm Merlyn, who secretly recovers Savage's remains after he is turned to ash in the final conflict.
Approached by Rip Hunter to be part of his time-travelling team, Ray Palmer seeks Oliver Queen's advice, and decides to join. Sara Lance, given the same offer, spars with her sister Laurel, who encourages her to go and be a hero. She gives Sara a new codename, "White Canary", and a new suit to go with it that doesn't include a mask. Martin Stein, Jefferson Jackson, Kendra Saunders, Carter Hall, Leonard Snart and Mick Rory are also recruited, all in order to stop Vandal Savage from conquering the world in the year 2166. They travel back in time to 1975 to meet Dr. Aldus Boardman, an expert on Savage, whose information would later help Team Arrow and Team Flash defeat Savage in 2015.
At their first encounter with Vandal Savage in 1975 Norway, Rip Hunter's team find him selling a nuclear warhead at an illegal arms auction; one of the bidders is Damien Darhk, looking the same as he does in 2015, backed up by H.I.V.E. "ghosts".
While testing the Tachyon prototype to increase his speed, Barry Allen accidentally travels to National City on Earth-S and meets Kara Danvers, helping her to defeat the Silver Banshee and Livewire before she helps him return home split seconds after he left.
Barry visits Oliver at Laurel's grave, apologising for missing her funeral due to Zoom. Oliver vows to kill Damien Darhk in revenge, and asks Barry to leave before weeping over Laurel's grave. (This is the flash forward scene from "Green Arrow".)
Rip brings the team back to Central City in 2016 - but five months after they left. Sara returns to Star City, where her father tells her of Laurel's death. Rip tells Sara they can't go back in time to save her. Sara and Quentin visit Laurel's Grave where Sara reveals it was Laurel that convinced her to join Rip's team, and she will continue for her sister. Meanwhile, Professor Stein reunites briefly with his wife Clarissa
Barry goes to Star City to talk with Felicity about the changes that he has noticed as a result of Flashpoint. Team Arrow are unaffected, except that John Diggle and Lyla Michaels have a son - John Junior - instead of daughter Sara.
Nate Heywood notices changes to the timeline, and seeks out Oliver Queen, whom he has worked out is the Green Arrow, to help him find the Legends. They find Mick Rory in stasis on the Waverider under the sea. When they wake him, Mick tells them the Legends were scattered after attempting to stop Damien Darhk from blowing up New York with the Nazis in 1942. Oliver convinces Nate to join Mick in finding the others, while Darhk is revealed to have teamed up with Eobard Thawne.