This morning’s news of the Supergirl/Flash crossover has sent fans into a giddy tailspin, and rightfully so. Grant Gustin and Melissa Benoist have embodied their characters in a way that they’ve never really been before. A lot of people are asking how is this going to work? Well, let’s see...
The Flash/Arrow-verse and Supergirl-verse are one and the same.
Let’s get this one out of the way first. While this possibility is plausible, it’s impractical. Supergirl has heavily implied that Kal-El was the world’s first superhero, if not it’s only hero (before Kara’s public debut at least). Meanwhile, the Flash and Green Arrow are very well known in their respective cities. Without some severe retcons, this is an unlikely possibility.
Likelihood of Happening: 1 lightning bolt out of 5
Barry finds himself is Kara’s universe after a fight with Zoom.
Now we’re getting into one of the two most likely scenarios. This season of the Flash is all about alternate realities. It would be pretty simple for a fight combining Barry and Zoom’s speed sending Barry careening off into a third, yet-undiscovered universe, Kara’s. The plot from here would be simple- Barry aids Kara with her alien of the week, while she helps him get home. This would also allow Barry to interact extensively with Kara’s supporting cast, especially (I hope) J’Onn.
Likelihood of happening: 4.5 lightning bolts of 5.
Kara is shot into the Flash-verse during an alien fight.
Almost equally likely is Kara’s alien of the week fight results in her and the fugitive/invader popping into Central City in the Flash-verse. While J’Onn and Alex try to locate them, Barry and Kara team up to stop the alien, while the SuperSTARs find a way to get Kara home. I think this is slightly less likely than the previous only because the crossover was announced with Grant appearing in Supergirl, but not other members of the Flash cast.
Likelihood of happening: 4 S-shields of 5.
Grant will be playing the Supergirl-verse’s Barry Allen.
Here’s one that possible but unlikely. Why even have a crossover if it’s not the Barry Allen we know and love? But the possibility is there. Grant could play another version of Barry, powered or powerless, who meets and helps Supergirl and the DEO in some way. If he’s powered, Kara could even inspire him to become this universe’s Flash. Again though, why bother bringing Grant in if this is the plot? Why even involve the Flash?
Likelihood of happening: 1.5 S-shields of 5.
The Flash is some sort of hallucination.
If it wasn’t being promoted as a crossover, I’d rank this higher. However, it could be possible that Barry could appear as some sort of alien-induced hallucination or distraction.
Likelihood of happening: 2 S-shields out of 5
Both shows are revealed to be the daydreams of their Glee characters, and Mister Shue shows up to lead them in a feel-good episode-ending sing-along.
Ahahahahahahahahahahahaha! Wait... wait... I can seriously justif- BWAHAHAHAHAHAHAHAHA! No... no I can’t!
Likelihood of happening: 0 lightning bolts of 5. Actually, make that -10.