Every Arrowverse Crossover Ranked From Worst To Best
3. Invasion!
The biggest Arrowverse crossover of them all at the time, Invasion! marked the first ever time that Arrow and The Flash crossed over with DC's Legends of Tomorrow and Supergirl on this scale. Naturally, there was only one threat big enough to make it all happen: Aliens.
Based on the legendary DC limited series from the late '80s, it focused heavily on the arrival of The Dominators and their apparent plans for humanity while also attempting to juggle the titular heroes from four different shows - an example of just how much the Arrowverse had grown in a few years. However, it also managed to mix in the fallout of The Flash's Flashpoint arc incredibly well while shifting gears in order to use its plot to give Arrow the 100th episode it deserved.
Though there were some issues - the time-travel jargon in the final installment was a little confusing, Cisco's behaviour was exhausting at this point and it was a little annoying that Supergirl never got her own episode - but none of them could take away from the truly larger-than-life feel that Invasion! possessed. Not only was it an experience that would have been every bit at home on the big screen, it exceeded expectations by ensuring that the first time Supergirl met all of her Arrowverse counterparts was a unforgettable one.
To this day, it remains perhaps the most underrated crossover of them all, but it was an example of how bigger can indeed be better. And, for the record, the Arrow installment is one of the best episodes the show ever produced.