The Flash showrunner Eric Wallace revealed plans for an epic (and better) Arrowverse crossover event that would've again involved the Multiverse.
From the first grand Invasion storyline where the heroes assembled against the Dominators all the way to the epic Crisis on Infinite Earths crossover that tied together the DC universe, the Arrowverse has no shortage of crossovers throughout its stellar run on The CW.
However, there were crossovers that didn't happen, such as the planned team-up of Superman & Lois and Batwoman and Stargirl's proper crossover with Grant Gustin's Flash.
Two Arrowverse Crossover Events Almost Happened
Speaking with Entertainment Weekly, The Flash showrunner Eric Wallace talked about two scrapped ideas for crossover events in the Arrowverse that would've been much better.
The Flash Season 9 had several crossovers with other shows, notably Supergirl’s Dreamer and Stephen Amell’s Green Arrow.
However, the final season wasn’t able to pull off one grand crossover event that would’ve featured the returns of characters from Supergirl, Batwoman, and Legends of Tomorrow.
Wallace admitted that he wanted to adapt The Blackest Night as the Arrowverse's final epic crossover event, explaining how it ties back to Season 8's Deathstorm storyline:
"Back in Season 8, we set up 'The Blackest Night' storyline with Deathstorm. When Deathstorm was defeated, the emotional vibrations went all the way back to the Netherverse and another dimension to Nekron, who's right out of the comic books."
In DC Comics, The Blackest Night is a mini-series first published in 2009 that involves the Green Lantern Corps. It involved Nekron unleashing the Black Lantern Corps on the universe.
Wallace said that he had an ambitious vision to bring almost everyone back (yes, including dead characters):
"I wanted to have one final, big, huge epic crossover, getting everybody — if you're on a show or not — back together for that storyline. What that would have allowed me to do is bring back characters that are dead."
Wallace said that he wants to bring all the DC heroes together from The Flash, Superman & Lois, Titans, and Stargirl for The Blackest Night event. Sadly, it didn't come to fruition:
"The idea was to get them all together to stop Nekron and all his Black Lanterns, which I'm sure Geoff Johns would've loved because it's his creation."
Seeing The Blackest Night crossover with new heroes from other shows would've been a better and exciting option for the Arrowverse's final crossover.
Wallace also revealed that he also wanted to explore an Arrowverse crossover centered on The Forever War, confirming that such an event would've kicked off The Flash Season 10:
"That's one of these crazy things that I've been hinting at, which is very tied in with the Chronarch. We've been hinting that the Chronarch would be back in some way, as early as Season 7 when Abra Kadabra [David Dastmalchian] mentions to Barry, 'The Chronarch is coming and is going to mess up your life.' It has to do with Barry and Iris because eternity is falling apart and forever is getting taken away. That would've kicked off season 10 with a couple of special guest stars that we would have seen."
Interestingly, the Chronarch War (aka the Forever War) was referenced several times already in The Flash.
In Arrowverse canon, the Flash and the rest of the heroes went into battle against the Chronarch in 2049, with most of the fight taking place off-world.
While the Arrowverse's Justice League managed to defeat the Chronarchs, Flash and some heroes remain off-world to clean up the mess from the war.
Predicting How the Scrapped Arrowverse Crossovers Happen
Eric Wallace's confirmation that The Blackest Night storyline was the supposed final Arrowverse crossover hinted at how epic the finale could have been, especially after the reveal that characters from Superman & Lois, Titans, and Stargirl would be involved.
It would've been a delight to see Grant Gustin's Barry Allen interacting with Brec Bassinger's Stargirl while also seeing the dark and gritty Titans team be incorporated into the Arrowverse's different and happy environment.
Moreover, seeing a proper team-up between Barry and Tyler Hoechlin's different Clark Kent from Superman & Lois would've been hilarious and incredible at the same time.
The Blackest Night storyline could've also allowed the Arrowverse to finally pay off John Diggle's Green Lantern storyline that was teased all the way back to Arrow's series finale.
Meanwhile, The Forever War storyline would've featured more interaction between Barry and Melissa Benoist's Kara Danvers aka Supergirl, a team-up that fans last saw during Crisis On Infinite Earths.
Exploring the Arrowverse's cosmos could have also been an exciting storytelling opportunity if The Forever War was adapted on-screen.
The Flash Season 9 is available to stream on The CW app.