[Spoiler Warning: This post is full of plot details from Captain American: The Winter Soldier. For non-spoilers, here's why the latest film gives the Marvel Universe exactly the kind of reboot you didn't know it needed.]
Like every Marvel movie in The Avengers franchise, there are post-credits scenes in Captain America: The Winter Soldier for those who wait. Here it is, if you left the theater early or want to see it again.
This time, we see Hydra agent Baron Wolfgang von Strucker talking with another operative in a hidden lab about the fact that all of the secrets of SHIELD and Hydra have been released on the internet for all to see (not to mention, “trending” according to Black Widow).
Baron Strucker reassures his fellow Hydra agent that the only secrets revealed were the ones Fury and his team knew about. There are still several Hydra locations working on projects that SHIELD didn’t know about.
At this point, Strucker says they have something that is worth more than any of them ever knew. We then see Loki’s staff, the one used to kill Agent Colson in The Avengers. He says they have only scratched the surface on what they can do with it.
Baron von Strucker says they will keep Captain America and his “colorful friends” busy with some of the many other Hydra labs, so their more important work can continue.
They continue walking and discussing developments with their volunteers. Those killed in the experiments will be “buried so deep their own ghosts won’t be able to find them.
When the other scientist asks about “survivors,” the camera pans to show two prisoners, referred to as “the twins,” in clear cells. The young man is rapidly bouncing off the walls of his cell, while the young woman sits on the floor controlling several blocks floating in front of her.
Von Strucker says it is no longer the time of spies or even heroes – we have entered “the age of Miracles” and “there is nothing more horrifying than a miracle.” The girl claps her hands together and the blocks fly.
“Miracles” appears to be how mutants will be referred to in the Marvel universe – outside of the X-Men franchise owned by Fox. In relation to Marvel movies, owning the X-Men gives Fox exclusive rights to the word “mutant.”
The twins are actually Quicksilver and Scarlet Witch. This article from Screen Crush gives you a lot of background on the two and the roles they may play in the upcoming movies in the Marvel Universe.
They are the children of Magneto (yes, that Magneto, which one would assume would go unnamed in these movies) and have been part of the Avengers at several different points in the comics, despite starting off evil.
As far as a brief summary of their abilities, Quicksilver can move and think at superhuman speeds and Scarlet Witch can alter the probability of things with hexes.
While that sounds innocuous, in reality she is extremely powerful with the ability to explode things, stop bullets or projectiles and create forcefields among other things. Since they show her levitating blocks, it appears she may have telekinetic powers in the films.
Here’s a video discussing the post-credit scene and giving you some background comic book info on the two.
There’s also a second post-credit scene that shows Bucky (aka the Winter Soldier) in the Smithsonian learning about Captain America and his own fate. He realizes that Captain was telling the truth.
If you are looking for other Easter eggs in Captain America: The Winter Soldier, here is a list of 16 interesting scenes to keep an eye out for when watching Marvel’s latest blockbuster.