All eyes are currently on Avengers: Infinity War, the movie that boasts just about every character in the Marvel Cinematic Universe. However, just because it has the most characters doesn't mean it's the only MCU film with notable character returns. Just yesterday, Marvel announced the full cast for Captain Marvel, which just so happens to include one Clark Gregg, aka Agent Phil Coulson, making his grand return to the big screen. Ronan and Korath are back too, but there's a reason that isn't quite as notable as Coulson.
After dying in The Avengers, Coulson was resurrected to headline the Agents of S.H.I.E.L.D. TV show on ABC and hasn't appeared on the big since, making his return in Captain Marvel extremely notable. Captain Marvel takes place in the 90s, meaning that this is a younger, pre-Iron Man Coulson, long before he was ever on the wrong end of a magic scepter. However, it's the time period of the movie and the means of Coulson's resurrection that should be really important here, because all of this could be signaling the present-day return of Coulson and potentially the rest of the S.H.I.E.L.D. team, who are currently dealing with the destruction of the world on the show.
Given the ratings for the show, I'm going to gamble that not enough people are up to date with Agents of S.H.I.E.L.D., so let me give you a brief synopsis of Season 1. As we learn over the course of the series, Coulson was brought back to life by S.H.I.E.L.D. in the mysterious Project T.A.H.I.T.I., a fail-safe program meant to resurrect any fallen Avengers. The source of T.A.H.I.T.I. is the blood (plus a bunch of other weird science) of an alien corpse, later revealed to be a Kree. The Kree are pretty important in Agents of S.H.I.E.L.D., but they are also about to feature heavily in a movie called Captain Marvel.
Captain Marvel's origins are tied directly to the Kree. She basically got her powers by having her DNA merged with a Kree warrior named Mar'Vell (played by Jude Law in the movie). That's essentially the same thing that happened to Coulson, only instead of getting superpowers, he came back to life. Still a good deal!
The Kree will play a big role in Captain Marvel. Their war with the shape-shifting Skrull will serve as a backdrop of the movie, but mainstream audiences will be getting their first taste of what Kree genetics will do, which creates the perfect opportunity to bring Coulson back into the fold. Perhaps more importantly, it also gives the MCU the opportunity to introduce Kree genetics on a much larger scale for other purposes.
Chances are, a good number of people who watch the Marvel movies don't also watch Agents of S.H.I.E.L.D., which means those people may or may not have any knowledge about Agent Coulson coming back to life -- unless they casually read up on stuff they aren't watching. What's intriguing to note is that, by placing Coulson in such a Kree-heavy movie, Marvel could be sneakily creating a shortcut to get him to back on the big screen without actually addressing the events of Agents of S.H.I.E.L.D. in detail. If audiences learn that Kree blood does weird things to humans, then if Coulson comes back in, say, Phase 4, and alludes to the Kree as the reason he's alive, it will be much easier for audiences to accept that or accept anything else the MCU may want to do with Kree blood in the future.
Coulson isn't the only member of S.H.I.E.L.D. appearing in the movie. Nick Fury is back as well, and while he is largely there to meet his first superhero, he does offer a nice side bonus. Continuity-wise, this could be where Fury learns about the properties of Kree blood and begins to develop T.A.H.I.T.I. after seeing firsthand what it can do to a typical human. It likely wouldn't be overtly stated, but it's definitely nice headcanon.
It's much easier to reference a past movie than it is to reference five seasons of a TV show. Not to mention that Marvel Studios and Marvel TV are two entirely different entities and it's not as simple to crossover as one might think. (Although big screen characters have appeared on the show occasionally.) Coulson is unique because he was originally a movie character, so he can theoretically jump between both worlds, although there's never really been a good opportunity until now for him to do so. Putting him in this movie is actually kind of genius because not only can he realistically show up in the 90s with little explanation, but also Agents of S.H.I.E.L.D. has been toying with the concepts that could be introduced in Captain Marvel for years now.
If Coulson were to return to the present-day MCU sometime down the line, there's a chance that his teammates from Agents of S.H.I.E.L.D. could tag along with him. If S.H.I.E.L.D. doesn't come back for Season 6, it certainly leaves room in those actor's schedules to make appearances in movies. Previously, people involved with Avengers: Infinity War have called intermixing the TV characters into the theatrical world "impossible," but if Coulson can do it, there's a chance that Daisy Johnson and Melinda May could, as well.
While fans have been anxiously awaiting a reunion between Coulson and the Avengers, there's more than just that reason to bring Coulson back into the fold. In Phase One, he was the glue that held the sails together. We're entering new, uncharted territory after Phase 4, and a familiar face like Coulson may just be what we need to keep this new era of the MCU together or he may be the bridge we need to accept a new Phase of Marvel movies that does a lot of interesting things with Kree blood.