[Mild SPOILERS for The Flash/Supergirl crossover ahead.]
The CW has been building its shared DC Comics universe over the past few years, first by establishing Arrow, then spinning off Central City's CSI tech Barry Allen (Grant Gustin) into his own series on The Flash. The most recent addition is Legends of Tomorrow, which combined characters from both Arrow and The Flash with new heroes in order to establish an ensemble comic book series. Also under the umbrella of DC shows created by producer Greg Berlanti is Supergirl on CBS.
Recently, The Flash established that Supergirl is part of The CW's DC Comics universe as one world in a multiverse. Prior to that reveal, CBS confirmed there will be a crossover between The Flash and Supergirl that will see Barry visiting Kara Danvers (Melissa Benoist) in National City. Now we have the first set photos from the crossover episode, which tease a villain team up in addition to the partnership between The Flash and Supergirl.
The photos posted on Twitter (below) depict both Gustin and Benoist suited up in their costumes for The Flash and Supergirl. But, also making an appearance are Italia Ricci as Siobhan Smythe a.k.a. Silver Banshee and Britt Morgan as Leslie Willis a.k.a. Livewire. Take a look at the set photos from Supergirl's 18th episode in season 1, titled 'World's Finest':
— DCnaTV (@UniversoDCnaTV) February 23, 2016
— The Flash Hypnoweb (@Flash_HW) February 23, 2016
— La Tercera (@latercera) February 23, 2016
Leslie was introduced in episode 4 (what would have been episode 5, but the two were swapped due to real world events) of Supergirl season 1 and hasn't returned since being defeated by National City's hero. Siobhan was more recently introduced as a workplace rival to Kara, though she will make her debut as Silver Banshee later this season.
Although the set photos for the crossover between The Flash and Supergirl show the heroes in action (as opposed to the selfie previously posted by Gustin) the scene they depict offers more questions than answers. We still don't know the reason behind or the how of Barry traveling to National City. Certainly, events of The Flash's 'Escape From Earth-2' episode, which saw the S.T.A.R. Labs team close the last breach between the universes and Jay Garrick captured by Zoom on Earth-2, could provide a motivation for opening a new breach - one that takes Barry to Supergirl's world rather than Earth-2.
Of course, in terms of definite answers, the set photos do show that Supergirl and The Flash will team up to take on the villainous team of Silver Banshee and Livewire - though how those two meet or the reason Supergirl actually needs The Flash's help with that fight are less clear. Still, with little more than a month left before the crossover airs at the end of March, there's plenty we don't know about the episode. Whether 'World's Finest' will fall into the category of a less successful crossover - like, arguably, certain Arrow and The Flash crossovers - or an entertaining story that fits into both shows' timelines, remains to be seen.
Supergirl airs Mondays @8pm on CBS. The Flash airs Tuesdays @8pm on The CW. Arrow airs Wednesdays @8pm on The CW. DC’s Legends of Tomorrow airs Thursdays @8pm on The CW.