For those of you who don't know, CBS made a quick decision to bring a Supergirl television show to series. With the pitch being about Superman's youthful cousin coming into her powers and becoming a superheroine in her own right, the potential series has gotten people talking. With the addition of Greg Berlanti from the CW's Arrow and the Flash, fans have begun to speculate about what might be.
With two successful shows on CBS's sister network, the CW, many are speculating that the show may find itself crossing over with the Flash and Arrow. When asked about the possibility of a cross-over, Berlanti said, "So much has to go right for us to be able to make a great show. Again, I think of myself as like if I were watching them, I would want to see that. But we have to get so many things right to make a good show and so much of it is luck, unfortunately." While that isn't a definite no, it does set the expectation that fans shouldn't hope for it in the immediate future, although Grant Gustin, who plays Barry Allen, the titular Flash, has expressed interest in the idea.
Two longstanding members of the Superman supporting cast, Jimmy Olsen and Cat Grant, have been confirmed as characters in the series. As a result, there's been a lot of buzz about the potential for Superman himself to appear. While this would be an easy way to boost ratings, it might actually be a mistake.
People seem to be expecting Henry Cavill, the star of Man of Steel and many other future films in DC Comics' blossoming film franchise, to turn up as Kara's cousin. While this is possible, it is unlikely, since Berlanti was part of the team that made it clear that the two CW network series did not tie in with the films, and that the two universes are separate. Unless Supergirl was crafted specifically to tie into the cinematic universe, in the same vein as Marvel's Agents of SHIELD, it's a safe bet to assume that this show will be separate as well.
If Supergirl ties in to Arrow and the Flash, then it should follow the same idea of using less prominent characters. The television universe could be used to flesh out a lot of lesser-known characters rather than spending time reestablishing Batman, Superman, and Wonder Woman. In doing so, the shows could prove to the general populace that these characters can pull their own weight, expanding their fan base to reach more than just the avid comic book readers who are already aware of this. From a business perspective, promoting more obscure characters could increase sales on their respective titles. If someone's not buying Superman, Batman, or Wonder Woman, it's safe to say that an appearance on a television show isn't going to change the sales of their comic, due to the worldwide recognition of their characters. These less widespread heroes appearing on one of these shows actually could make a difference for their titles, as they are an unfamiliar character being introduced, rather than a familiar character being reintroduced.
Most importantly, Supergirl should be able to hold her own series. Although it didn't follow the same Supergirl, Peter David's seven year run proved that a Supergirl is capable of holding her own on a title without a major crossover or appearance by Superman. During that series, Superman was rarely a guest. If the two were going to be seen together, it was likely to be in the pages of one of Superman's numerous solo titles. If this is true for one Supergirl, why can't it be true for Kara?
I'm not saying we should never see Superman on the show. I'm just thinking that they should establish Kara as her own character first, and maybe have Clark show up later in the series. It's important to keep in mind that the series that CBS ordered is Supergirl. They're going to flesh out and explore the character in any way they can. An essential part of Supergirl leading her own series is establishing the idea that Superman does not make Supergirl. Yes, she named herself after her cousin, but she is a strong, intelligent character in her own right, and worth watching based on her own merits, not what guest star will be on this week.