It seems that for every thing we learn about Justice League, we're unsure about two more things. The latest point of confusion (aside from Henry Cavill's mustache dilemma) stems from the film's SDCC trailer. While Superman's return was pseudo-confirmed in the trailer, we're not too sure who we actually saw. Take a minute (or four) to refresh yourself on the trailer before we continue:
We're obviously supposed to assume the figure at the end of the trailer is Superman. He's confirmed to return, and Warner Bros. wants general audiences to know they'll be getting the full League without spoiling his appearance. It's the perfect way for Warner Bros. to have cake and eat it too. That is, unless it's not Superman at all. In fact, I'd go as far as saying that the figure is his cousin, the far more interesting Supergirl. Here's why:
Bruce's Slender Hologram
Living up to his title as the World's Greatest Detective, we see Bruce Wayne silently judging a hologram of what appears to be Superman. Upon closer inspection however, the figure doesn't match Henry Cavill's bulky frame. It's much more lithe than what we're accustomed to, looking more like a teenage girl than a fully grown man. Say, how many Superman-esque teenage girls are there?
Batman researching Supergirl would make sense given the circumstances. The world has to prepare for another alien invasion, and their "only" line of defense is a rich martial artist, a demigod, an underwater king, a human-robot hybrid and a speedster. Not totally hopeless, but far from a guaranteed victory. Bruce likely explores options to bring Superman back to life, visiting the Kryptonian scout ship in the process. It's here that he stumbles upon Kara Zor-El, or at the very least, learns of her existence.
The House Of El And Hope
The ending of the latest Justice League trailer has thrown fans for a loop. Alfred is working outside at night when his glass of whiskey begins to shake (a la Jurassic Park). The shaking is caused by the arrival of someone (or something) whom Alfred addresses immediately:
He said you'd come. Now let's hope... you're not too late.
Though context and logic point towards this being Superman's late-in-the-day arrival, given the emphasis on hope (the Kryptonian meaning of the House of El's crest) and the hint of a red cape in the corner of the screen, viewers weren't so quick to believe what they were given. Superman's steps haven't made such an impact this far, and surely Warner Bros. would go out of its way to not spoil a surprise character (especially after the backlash to Batman v Superman's "Doomsday trailer").
Fans quickly theorized we were actually seeing Cyborg (hence the thuds), Aquaman (finally answering Bruce's calling), or Green Lantern (the green reflection in Alfred's glasses). Neither option works however, as Cyborg's shiny armor isn't visible, Aquaman wouldn't know Alfred, and a green reflection in glasses is a common phenomenon (ask any bespectacled person and they'll confirm).
The only character who checks off all the boxes here (aside from Superman), is his cousin Kara. Both don red capes and the House of El emblem, matching the corner-shot and emphasis on hope in Alfred's line. The heavy steps also make sense, s Kryptonians have trouble controlling their powers when first being exposed to a yellow sun (as seen in Man of Steel and countless DC comics). As for who said she'd come, it's likely Bruce mentioned his research to Alfred and told him about her impending arrival. Nothing like an invading army to give you a wakeup call
Persisting Rumors Of A DCEU Debut
Although Kara Zor-El isn't the biggest Kryptonian name in the DC pantheon, her popularity is steadily rising thanks to the Supergirl TV series on the CW. If some rumors are to be believed, that's enough of a reason for Dc to introduce the character to its cinematic universe. Most reports and "leaks" indicate she'll be making her debut in the long-awaited Man of Steel sequel, but these rumors are refuted by other outlets almost as quickly as they're "revealed."
With the film being so early in its development, it's very likely that her character's role (should she have one at all) is still in flux. It's possible her introduction was moved up to Justice League, and her training and development will remain in Man of Steel 2. After all, where there's smoke, there's fire. And this smoke just doesn't fade away.
She Already Exists In The DCEU
For all the frenzy surrounding Supergirl's role in the DCEU, it's easy to overlook the fact that her existence has already been confirmed twice. The first confirmation came in the form of a canonical prequel comic. In it, Kara Zor-El is an unspecified relative of Kal-El who was tasked with colonizing other planets on behalf of Krypton. After the 10-year hibernation period, she awoke to find her crew had been murdered by her former classmate (just as he had killed Kara's boyfriend). Being so close to a yellow sun, the two had a superpowered fight inside the ship, causing it to malfunction and crash-land on Earth. This scout ship is the same one visited by Kal-El and Lois Lane in Man of Steel.
While the comic confirms she landed on Earth, the film takes it one step further by teasing her survival. When Superman enters the ship, he comes across four pods. Three of them hold skeletons (referencing the deceased crew), while a fourth one is open and empty. When asked if the open pod references Supergirl, director Zack Snyder said this:
No. [Laughs] I’m not going to say anything but, it’s a thing.
The initial denial may sound like a clear answer, but the laugh and decision to "not say anything" indicate there's more to this than meets the eye. The shot was also left in intentionally, according to writer David S. Goyer:
There’s a shot there – and, it’s funny, at one point Zack took it out, but I cried ‘Uncle!’, and he put it back in. But you see there are four pods: three of them have skeletons in them, but one is open and there is no skeleton. Zack had missed it the first time he read the script. I pointed it out to him, and he was like, ‘Okay, that’s interesting. That’s an interesting loose end.
Loose ends are a constant in shared universes, and are often picked up on in future films. Perhaps this time, that "future film" will be Justice League. Should Supergirl be in the movie, her role will likely be kept secret until the film releases in November. While there's no way to be sure that the Girl of Steel will be squaring up against Steppenwolf and his army of Parademons (yet), it'd be a great way to subvert audience expectations and capitalize on the character's success.