The Avengers: Doomsday Trailer Makes It Clear That One Marvel TV Show Is Required Viewing

Are you ready to do your Marvel Cinematic Universe homework all over again? If your experience is at all like mine, the release of any new movie in this franchise tends to come with a boatload of questions from family and friends about what may or may not be "required viewing" this time around. The upcoming release "Spider-Man: Brand New Day" is a relief because, even despite a major cameo or two, it seems like you really only need to have seen the very last Spidey movie to be up to date — what a concept! With Marvel's other big release this year, well, that's a different story altogether. "Doomsday" is truly upon us, and the new "Avengers" trailer gives us one surprising indication of what we'll need to watch beforehand.

Fans likely had a feeling this would be the case. There's the obvious caveat that "Avengers: Doomsday" will only make sense if you know what went down in both "Infinity War" and "Endgame," of course. Considering those are two of the highest-grossing movies ever, we can't imagine that poses much of an issue. And then there's the metatextual aspect of needing to have a baseline familiarity with the original "X-Men" movies under 20th Century Fox, as several of the cast return as multiversal variants of themselves. The focus on characters from "Thunderbolts*" and "Black Panther" and "The Fantastic Four: First Steps" makes things a little more complicated.

But did you happen to catch one key shot featuring a fan-favorite character? Tom Hiddleston indeed reprises his role as Loki, but with a twist. He's holding a funny-looking badge and wearing an oddly ungodlike outfit ... which checks out, for those who've actually seen both seasons of the Disney+ "Loki" series. If not? Well, you might need to brush up.

Man, apparently even sacrificing yourself to save the Sacred Timeline and become the overseer of the entire multiverse by literally holding it all together at the End of Time doesn't buy you a get-of-jail-free card when Robert Downey, Jr.'s Doctor Doom comes knocking. If none of that makes a lick of sense to you, then chances are you're probably scratching your head over the return of Loki about halfway through the "Avengers: Doomsday" trailer. The trickster god who memorably died at the hands of the Mad Titan Thanos early in "Infinity War" did come back again in "Endgame," but only thanks to the magic of multiversal time travel. The last we saw of him, he'd gotten his hands on the Space Stone and teleported to places unknown.

The Disney+ series "Loki" exists to answer that lingering question, bringing this variant to the halls of the Time Variance Authority — essentially, the MCU's version of time cops whose one job is to prevent the breakdown of the multiverse by "pruning" universe-hopping troublemakers. Season 2 dove even deeper into the multiverse mayhem of it all, steadily building up to one of the most satisfying (and conclusive) endings of any installment of the MCU. But, wait, is "Doomsday" now undoing Loki's final arc just to add another cameo into a jam-packed blockbuster? Will even this self-contained moment be rendered meaningless, just because yet another villain is running rampant? Will this franchise truly never allow any character to rest?

Technically, the new trailer gives absolutely no answers to any of these pressing questions ... but we have some suspicions on how Loki might end up in the middle of the fray all over again.

As far as trailers go, the "Avengers: Doomsday" footage is keeping a tight lid on exactly how the plot of this blockbuster will unfold. All we know for sure is that the next major threat to the MCU is here, Thor (Chris Hemsworth) is the only one who seems to know what they're up against, and he must spend a significant amount of time bringing Earth's mightiest (but scattered) heroes together again to even stand a chance. By all accounts, that means going on a reunion tour for the ages, highlighted by Chris Evans' return as Steve Rogers.

But could that help provide a hint as to how Loki winds up back in the thick of it, as well? Although there was some behind-the-scenes confusion about this, the accepted explanation is that Steve traveled to an alternate branch of reality at the end of "Endgame" to live out his retirement with Hayley Atwell's Peggy Carter. Now that he's once again called back into action to help save the day, it stands to reason that everyone else would be fair game — including the likes of our favorite god of mischief. But how can he leave his newly-installed post as the guy who's keeping the entire multiverse from falling apart.

Well, it's possible Doctor Doom poses an even graver threat to the multiverse. Depending on what his evil scheme actually entails, who better to bring in than an actual multiverse expert like Loki? And, if you believe those plot leaks regarding "Doomsday" and "Secret Wars," the creative team may have come up with a clever way to tie both Loki and Steve Rogers together. We'll see when "Doomsday" arrives on December 18, 2026.