Next week, we'll see something that has been in the works since Supergirl first soared onto our screens - The Flash comes to the Supergirl universe!
Grant Gustin's Flash will find himself on Kara's Earth - presumably looking for a way to get to Zoom on Earth-2. He may be using his speed to cross the barriers between worlds, but all we know for sure is that he winds up in National City, and needs Kara's help to get home. Meanwhile, Kara needs Barry's help to take down two villains at once: Banshee and Livewire.
It looked like this was going to be a one-off crossover, but now in a recent interview with Entertainment Weekly, Grant Gustin hints that this could be the start of multiple crossovers with the rest of the CW superhero world.
That’s in the cards at this point. The whole point of us doing this crossover is setting up the fact that maybe next year we can cross over all of them.
With Supergirl in different universe (not to mention filming in a different city!), we know that Kara won't be able to join Oliver and Barry in the constant crossovers that we see between Arrow and The Flash. Still, there's nothing to stop her appearing in the occasional episode - taking down the biggest of bads with the small-screen mini-Justice League that the CW has going on right now!
Legends of Tomorrow is also in on this potential massive crossover - although we haven't seen the Legends gang in Star or Central City since they left, they are sure to resurface at some point in the future (or the past... time travel jokes are fun!).
If Supergirl does join the rest of DC's small screen characters, presumably she would have to leave her Earth (and LA) and head to Earth-1, if only because that's where everyone else is! If Barry finds a way to speed through the barriers between worlds, Supergirl could presumably do the same thing. After all, it would be a lot less likely that Barry brings all of Team Arrow and the Legends over to Kara's Earth!
Obviously for right now, this is still in the realm of speculation - fan reaction to 'World's Finest' is going to have an impact on future crossovers, along with future storylines and the successes of each show individually. However, it's still exciting to think that we could be building toward a small-screen Justice League! There have been hints that Green Lantern might come to the Flarrowverse in future, along with rumors that Matt Ryan's Constantine could join the Legends next season.
All in all, it seems like the CW and Berlanti dream team are cooking up something big - and we can't wait to see it! In the meantime, we'll be on the edges of our seats for 'Worlds Collide' next week.
"Worlds Collide' airs Monday the 28th