Not long after the credits for the film start scrolling, the midcredits scene begins. In it, we find ourselves in the top-secret lab in the Avengers compound that we've seen in past Marvel films, where Steve, Nat, Bruce, and Rhodey are dealing with the aftermath of Thanos's Avengers: Infinity War snap. While Captain Marvel takes place in 1995, this is clearly back in present day, and can't be much more than a day or two after the events of the snap.
Steve and Nat are staring in horrified shock at the screens around them, which are tallying the ever-growing number of people who turned to dust around the world. "This is a nightmare," Steve says, before Nat retorts, "I've had better nightmares." Obviously things aren't going so well for them. Fortunately, they do have a lead: Nick Fury's '90s-era pager.
Bruce alerts the pair that the device, which he's been monitoring since Fury's disappearance in New York, has stopped emitting the signal that it was initially, and they worry about what the pager is for or who it could be used to contact. But luckily, they don't have to wonder for long: Carol magically appears in her suit inside the lab, and asks the group, "Where is Fury?" So, yes: Captain Marvel can time travel, apparently? And infiltrate the Avengers compound without raising a single alarm? And do it all silently?
On top of that, her appearance is of note because it raises questions about when, exactly, it is — is her arrival before the footage we've seen thus far in Endgame trailers, or nah? And how will Steve incorporate Carol into his plan for the Avengers? We have to assume that she'll play a major role in helping the team defeat Thanos, if only so she can bring back her BFF Fury.
It all happens so fast that there's really not enough time to sufficiently ruminate on all the details of her hop forward in time, but it's exciting nonetheless.