The biggest reveal in the final Captain America: Civil War trailer was most certainly Spider-Man’s first-time MCU appearance. The fans have been waiting for him ever since the MCU concept first emerged, and every new week without the reveal just increased the fans’ expectations.

Were these expectations met? Well, that really isn't the point of this list. The point is to see what happened up to the time of this big Civil War reveal, and to shed some light on the less obvious details in the trailer. And, aside from the answer to the most important question of who will ultimately win the fight between Iron Man and the Winter Soldier, there’s one question that even now remains unanswered.

There is a scene in the trailer in which Captain America, Iron Man and Bucky Barnes fight. It can be argued that it isn't the final fight between them - but there is something happening in the background. Better yet, someone can be seen in the background.

At first the fans can believe that the most obvious answer is also the true one. But, at a closer inspection, those same fans will realize that they haven't got a clue as to who that person is and what is he or she is doing there.

Obviously, from here on you can expect spoilers!

The Winter Soldier – the obvious answer

The most obvious answer is that the Winter Soldier is in that stasis tube as the main antagonists of the movie battle it out. After all, some of the most poignant images in the trailer show Bucky once again brainwashed, in full Winter Soldier apparel, even with some upgrades. And it’s totally understandable for people to indeed believe that he is in that stasis tube.

Except he isn't - frame by frame, that Civil War trailer scene shows Steve's pal in the background, trying to take Iron Man down, trying to help Captain America. Later on, his endeavor will prove fruitless, since he will have his metallic arm ripped off.

So, even with the Winter Soldier at the height of his powers, Iron Man is just too much for him. And if he isn't in that stasis tube, who is?

Agent 13

In the comics, everybody knows that Steve Rogers meets his (temporary) end at the conclusion of the Civil War. The responsible party is, apparently, Crossbones, who snipes him. But there is also one other shooter, the one who actually did it, a person Steve Rogers actually trusted - Agent 13, Sharon Carter, Captain America’s girlfriend.

Apparently, Dr. Faustus brainwashed her into killing the superhero.

Obviously, there is no Dr. Faustus in the MCU. However, the idea of brainwashing people isn't new at all - after all, Bucky Barnes became the Winter Soldier after HYDRA used this procedure on him. So what if Sharon Carter is the person inside that stasis tube? What if Baron Zemo has captured her and now is trying to get her on his side?

Bucky Barnes will most likely try to keep that from happening to another person, while Steve Rogers has all the more reasons for saving her (after all, even if they are not a pair in the MCU, she is the niece of his former love interest).

On the other hand, Tony Stark might see brainwashing the heroes as the only possibility of bringing them to his side. So he also has a reason for wanting to keep her in the tube. But this is a rather thin argument - so maybe he is doing it out of spite.

Red Skull

The fans have been saying that the Red Skull would return since The First Avenger concluded. The character wasn't explored to his full potential, and the way in which he was eliminated was more than ambiguous. So even if Hugo Weaving doesn’t return to the role, the door needs to be opened once again. After all, the Tesseract functions like a literal one - what if Zemo found a way to bring the Red Skull back?

Even more, maybe he has already done it and maybe, right now, the Red Skull is in that stasis tube regenerating (after all, a huge explosion and instantaneous travel to the other side of the universe would surely leave some marks).

So maybe Zemo’s role in the Civil War is to usher in Captain America's greatest enemy, the founder of HYDRA, and the one who can orchestrate a war between Earth's mightiest heroes from behind the scenes.

But we won't bet on that. Tony Stark would have no reason to let the Red Skull wage war once again on Earth.

Just a clone

Thus far, the MCU hasn't presented us with this possibility - but we can’t exclude it…What if there’s a clone of Steve Rogers inside that stasis tube, someone who can tip the balance in HYDRA’s favor? It certainly wouldn't be impossible"¦

By now, the evil organization must have realized that the super serum was lost when its creator died. So the best alternative would be to replicate the next best thing - the human being on whom the super serum actually worked.

The Winter Soldier will be just a failed experiment that tries to prevent another. And Steve Rogers certainly doesn't want to meet his evil twin on the battlefield. As for Tony Stark, having a Captain America on his side could certainly further improve his chances of winning the Civil War.

Another HYDRA experiment

At the same time, this could be just another HYDRA experiment. As we know, the evil organization already created miracles. So what if they will try to do it again, giving birth to a supervillain who can obliterate the entire Avengers team?

HYDRA no longer has the Scepter - but this doesn't mean that its scientists haven't been put to good use. Even if it won't be some metahuman on the same level as Quicksilver and Scarlet Witch, the organization can at least try to improve the Winter Soldier by creating a better version.

Are there any candidates for this position? Of course there are. And Civil War certainly needs a super powerful villain to unite the Avengers once again.

One of the few still-living MCU villains

Another rumor that’s recently been circulating the web is that Civil War will bring back one of the villains previously left alive (there aren't too many of them, though). And since Civil War has brought back Thaddeus Ross"¦

Many fans believe that the general had enough time to perfect and refine the serum used on Emil Blonsky in the Incredible Hulk. By now, he has discovered that he can control the Abomination, switching it on and off, as needed. And, sure enough, the Abomination is the only existing supervillain on Earth who could pose a threat to the Avengers (minus Hulk and Thor).

So maybe it is Emil Blonsky in that stasis tube, with Iron Man defending him. Yes, it is a HYDRA installation - but this can be easily explained if Zemo is manipulating everybody from behind the scenes. If it is indeed so, an Avengers vs. Abomination showdown is more than welcome!

Quicksilver

Marvel can't keep its heroes dead - so the Civil War might bring the resurrection of Quicksilver. Even if Joss Whedon said that the character was definitely dead in the MCU, Avengers: Age of Ultron also revealed the means of resurrecting metahumans, using the same apparatus that healed Hawkeye. Take into account Quicksilver's own regenerating ability (as seen when the the soldiers shoot him) and we might have an answer.

As seen throughout all of the MCU movies, HYDRA pops up everywhere to gather artifacts. So maybe the organization has also acquired Quicksilver's body and is now trying to resurrect it. We don't know how that will work though, since Scarlet Witch has already chosen a side, but the speedster can always be brainwashed.

But we do know that Tony Stark, especially if he is manipulated by Zemo, has every reason to want Quicksilver on his side.

Another hero for Civil War

Lastly, there is one other possibility/opportunity for the Russo brothers, and that is to introduce yet another superhero in the MCU, one who could only pop-up in the end, after the entire Civil War has ended. This superhero might be seen, in the end, as a symbol of peace.

So who could that be? If we look at the MCU slate, we see that almost everybody has been introduced, with Black Panther and Spider-Man already involved in the Civil War. So what if Captain Marvel is the one created in that stasis tube?

As we know, Carol Danvers received her powers after encountering the Kree superhero Captain Marvel, and after her DNA fused with the superhero's DNA. As we know, the Kree have been present both on both the big (Guardians of the Galaxy) and the small screens (Agents of SHIELD). So it wouldn't be too difficult for the writers to find a way to work them into the Civil War.

After all, HYDRA is pretty resourceful.

And even if the origin story is changed, introducing Captain Marvel in the Civil War is certainly something few have anticipated.

If we are to say anything more about this issue, we believe that it’s either Agent 13 or Captain Marvel in that stasis tube. What do you think?