Agents of S.H.I.E.L.D.'s Phil Coulson is dead, but that hasn't stopped him before. According his partner Agent Melinda May, she was with him until the very end, but the Season 6 trailer teases another story for Coulson actor Clark Gregg. Coulson -- or someone who looks very much like him -- returns for the very brief cameo at the end of the trailer, but he doesn't appear to remember the events of the series so far. When someone asks him if he's from S.H.I.E.L.D., he simply responds, "Never heard of it."
Of course, Coulson is no stranger to death. He already died once in 2012's The Avengers, when Loki shoved his scepter through his heart. However, Nick Fury -- Coulson's director and longtime friend -- wasn't ready to let him go just yet. Using Kree biology and a secret experiment, his scientists brought Coulson back to life. This procedure would ultimately be undone by Ghost Rider in the Season 4 finale, leading to his death in Season 5.
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However, it looks like this Agents of S.H.I.E.L.D. death is going to stick this time. According to Gregg, he will play "this other very mysterious person, who is not Phil Coulson," in Season 6. Here are just a few ways -- both old and new -- that the show could explain away this Coulson doppelganger.
Time Travel
Considering it was a major plot device in Season 5, time travel naturally tops the list. Last year, Coulson's team was thrust into the future by a Kree monolith. There, they discovered Earth had been destroyed, and they were told there was nothing they could do to stop it. Nevertheless, Coulson and his team traveled back to present day and successfully prevented Graviton from ending the world. By the finale, Coulson -- dying from an earlier injury -- bid his team a tearful goodbye and walked off into the sunset with May.
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As harrowing and tragic as the events of Season 5 were, the time loop had one major benefit. Though Fitz died in action in the season finale, an earlier version of him still exists. That is to say, he was not sent to the future with his teammates through the Kree monolith. With a little help from an alien anthropologist called Enoch, Fitz entered cryosleep earlier in the season and eventually "caught up" to the rest of the team. He returned to the present with the team, meaning that two versions of him existed simultaneously: the one who experienced the future and the one still in cryosleep. As glimpsed in the Season 6 trailer, the team will make good on their promise to rescue Fitz from cryosleep, which means he'll be back despite his death.
Of course, only one version of Coulson existed in this particular time loop -- that we know of, anyway. However, the team seriously meddled with the timeline, which could cause heretofore unseen consequences. For example, they may have created an alternate timeline, a storytelling device that has frequently cropped up in the comics. Perhaps the fallout rippled backwards, creating a version of Coulson that never joined S.H.I.E.L.D. and became unmoored from time. This probably isn't the most likely scenario, but it is worth mentioning since it was such a major piece of Season 5 and, possibly, Avengers: Endgame.
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The Multiverse
Agents of S.H.I.E.L.D. has toyed with the idea of the multiverse before, but the series hasn't really explored its potential -- at least, not yet. Season 4, which released around the same time as Doctor Strange, introduced the idea of the multiverse with the debut of Robbie Reyes' Ghost Rider. Like the Sorcerer Supreme, Ghost Rider can tap into the multiverse's energy and open portals to other dimensions. Likewise, in Season 5, Coulson's team had to deal with the Fear Dimension after the Kree monoliths exploded in the Lighthouse, opening a rift in space-time. This caused one world to leak into the other, allowing manifestations of the team's worst fears to wreak havoc on their bunker.
Since the multiverse has long since been established, Season 6 could take a deep dive into the implications of alternate universes. This version of Coulson may be from a dimension where S.H.I.E.L.D. doesn't exist or stayed underground. He could come from a post-apocalyptic world or one with technology so advanced that it has easily mastered the art of inter-dimensional travel. The possibilities here are truly endless. This seems like one of the most likely explanations for Coulson's Season 6 doppelganger.
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LMD
In the comics, Life Model Decoys are a S.H.I.E.L.D. favorite. Director Nick Fury, in particular, has an infamous LMD habit; if he senses danger, he'll send a LMD of himself instead of showing up in person. In fact, this particular trick has saved his life on several occasions -- and it could explain how Coulson returns on Agents of S.H.I.E.L.D.
LMDs debuted on Agents of S.H.I.E.L.D. in Season 4. Created by Dr. Holden Radcliffe, an LMD called Aida fostered the development of the Framework, a virtual world that erased the regrets of its users. This created a mess of a reality, where Hydra never fell, Inhumans were hunted down and our main characters were scattered across the world. Coulson's team ultimately destroyed the Framework, but at least one LMD survived until midway through Season 5: Anton Ivanov, aka the Superior (or was it MODOK?).
Though Ivanov ultimately met his end at Yo-Yo's hands, his survival could mean that other LMDs managed to survive the destruction somehow. What's more, he had plenty of time to build more LMDs like himself and stored them away in case of emergency. If this is the case, his archive would likely be incomplete, considering the destruction of the Framework and all its facilities. As such, a Coulson LMD could be reprogrammed with a completely different backstory. Indeed, it may not even know it is based on someone else. This would explain why Season 6's Coulson doppelganger doesn't know what S.H.I.E.L.D. is.
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Skrulls
Captain Marvel is just around the corner and, with it, the Marvel Cinematic Universe's version of the Skrulls. The Skrulls, of course, are a race of shapeshifting aliens with a nasty habit of trying to invade Earth. Notably, Coulson will be heavily involved with the events of Captain Marvel, which takes place in the mid-90s. As such, he has some experience with Skrulls -- and the Skrulls will have some experience with him.
It will be hard to tell how Agents of S.H.I.E.L.D. will deal with the Skrulls until Captain Marvel releases in theaters next month. However, it's possible that a subtle Skrull invasion set in present day could lay the groundwork for Season 6's Coulson doppelganger. Perhaps this Skrull glimpsed Coulson during Captain Marvel and mimics his appearance when he returns to Earth on Agents of S.H.I.E.L.D. On the other hand, a Skrull could assume Coulson's appearance based off a picture, or a hologram like the one Mack uses in the Season 6 trailer. Either way, the Skrulls would provide an easy explanation for this mysterious doppelganger.
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Clone
Or Agents of S.H.I.E.L.D. could try something completely new. The show has borrowed quite a few comic book conventions over the years, but there's a major one it hasn't tackled yet: clones. As controversial as they may be, clones are a staple of comic book mythology, from Spider-Man's infamous Clone Saga to the X-Men's Madelyne Pryor and Wolverine clone X-23. By exploring clones, the series would wade into uncharted waters, but -- like the seasons that have come before it -- that could be exactly what the show needs. A fresh, MCU-inspired take on clones could also provide a succinct, compact story for the show's shortened sixth season.
Resurrection
Lastly, it's possible all of this is a misdirection of some kind. The show's stars could be trying to throw fans off in order to keep the mystery going. If that's the case, this could be a simple resurrection -- something Coulson is no stranger to. He was implanted with false memories the last time he was resurrected; if that process went wrong, he may forget everything, not just the process itself.
That being said, this is the least likely scenario. The show gave Coulson a poignant, emotional sendoff in Season 5. By resurrecting him (again), his return would cheapen this major moment in the MCU canon. As such, this is unlikely, but worth considering all the same.
Agents of S.H.I.E.L.D. is set to return for its sixth season in July 2019 on ABC with 13 new episodes; the series stars Ming-Na Wen, Chloe Bennet, Henry Simmons, Iain De Caestecker, Natalia Cordova-Buckley and Elizabeth Henstridge.