The Flash: All-Star Team Up Season 1, Ep 18
Barry is surprised when Felicity Smoak arrives from Starling City along with her boyfriend, Ray Palmer, who flies in as the Atom. They've come to visit S.T.A.R. Labs as Ray needs help with his suit. Their timing turns out to be fortuitous because it’s all hands on deck after a meta human named Brie Larvin unleashes hundreds of robotic bees to attack and kill her former co-workers, including Dr. Tina McGee. A group dinner with Barry, Felicity, Ray, Iris and Eddie turns into a disaster.
Arrow: Suicidal Tendencies Season 3, Ep 17
Dig and Lyla get some action (although not the kind they were expecting), the Suicide Squad pops up again, the League of Assassins continues to frame the Arrow for murder, Ray Palmer rubs everybody the wrong way, and the A.T.O.M. suit gets its first combat field test.
Arrow: The Brave and the Bold Season 3, Ep 8
Part 2 of the Flash/Arrow crossover. Part 1 is The Flash: Flash vs. Arrow, in which Oliver & the team visited the Flash to ask for S.T.A.R. Labs' assistance in analyzing a boomerang used as a murder weapon. Now, back in Starling City, tracking the boomerang winds up putting Arrow into the middle of an A.R.G.U.S. operation. [more inside]
The Flash: Flash vs. Arrow Season 1, Ep 8
Central City meets Starling City! The Flash teams up with the Arrow to take on a rage-inducing, bank robbing metahuman.