Supergirl started a month ago on CBS and made incredible ratings before slowly falling these past few weeks. Greg Berlanti, the man behind Arrow and The Flash, is also the creator of the show centered on Kara Zor-El, Superman's cousin.
However, it has been repeated over and over again that the three shows wouldn't crossover anytime soon. Here is CBS Entertainment chairman Nina Tessler's statement on the matter a few months ago:
“That’s a different network so I think we're going to keep Supergirl to ourselves right now.”
Nevertheless, Bleeding Cool stated today that according to a reliable source, a Supergirl/The Flash crossover is actually in talks at Warner Bros. This crossover would seemingly happen around the season finale of both shows in May. This is a frequent rumor giving that the CW is co-owned by CBS, facilitating appearances in the other network. But today, this rumor seems more and more plausible.
Why this sudden turnaround? I think the numbers are pretty equivocal. Supergirl started with 13 millions viewers and a 3.2 rating. Today, after 5 episodes, the show is at 7 million with a 1.5 ratings.
More than the numbers of viewers, ratings are the most important factor and a network like CBS has pretty huge expectations. It was predictable to see a little fall after the pilot but Supergirl lost nearly half of its audience.
If the rumor reveals itself to be true, it would be a disavow from CBS who trusted the show to shine on its own. But a lot of people, and I think I'm speaking for almost everyone, wanted to see Supergirl be part of the Arrowverse and were very disappointed.
How could 'Supergirl' fit into the Arrowverse ?
At this point only one possibility seems plausible: alternate universes. This year, The Flash introduced Earth-2 and the notion of multiverse. With the existence of Superman and aliens, it has been clearly stated that Supergirl is its own entity. If we are talking about a crossover with The Flash, the multiverse hypothesis only reinforces itself.
We could see a 'Crises on Infinite Earths' type of story, surely not as big but at least including 3 or 4 Earths. It would be a way to introduce Supergirl in a believable way as we have already seen with Jay Garrick, for example.
I don't know about you, but the perspective of seeing the Girl of Steel teaming up with The Flash and maybe The Green Arrow is really tempting. It would also admit Superman's existence, even if I doubt we'll ever see him. But who knows? The sky's the limit.