This article contains spoilers for What If…? Episode 9.

At long last, the Season 1 finale of What If…? has premiered on Disney Plus, following up on last week’s unexpected cliffhanger. And while the show began as purely an anthology series with no recurring plotlines between episodes, Episode 9 has gone in the complete opposite direction, calling back to every single episode before it for the climactic finale.

Episode 9 of What If…?, titled “What If… The Watcher Broke His Oath?”, begins with a return to the world of Captain Carter (Hayley Atwell), showing what’s become of Peggy since her last appearance in Episode 1. Once again, she’s playing out a familiar scene, fighting Batroc and his henchmen aboard the Lemurian Star, just like Steve Rogers did in the opening of Captain America: The Winter Soldier. But it soon becomes clear that this is much more than just a callback to a previous episode — the Watcher (No Time To Die star Jeffrey Wright) soon appears to recruit Peggy for the battle against the Infinity Stone-powered Ultron, and she’s far from the only hero on his list.

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What follows is a montage of Uatu returning to the worlds of past episodes, offering an all-too-brief glimpse of how things are going across the multiverse. Star-Lord T’Challa (portrayed by the late Chadwick Boseman) is fighting Ego on Earth, Pepper and Shuri are still working to overthrow Killmonger (Michael B. Jordan), and Party Thor (Chris Hemsworth) is fending off Ultron’s forces. There’s even a glimpse of an unfamiliar world in which Gamora is working with Tony Stark on Nidavellir — a world that was meant to be the focus of another episode in this season, only for that episode to be delayed to Season 2. But while her past may be a mystery for now, Gamora is summoned alongside Thor, T’Challa, Killmonger, and Captain Carter to help the Watcher and Doctor Strange Supreme (Benedict Cumberbatch) defeat Ultron. And thus, the Guardians of the Multiverse are born.

The Guardians of the Multiverse in What If...? Episode 9

While this ragtag band of protectors doesn’t feature returning characters from every Season 1 episode, the mere existence of a multiversal team-up is a welcome surprise. After all, What If…? originally seemed to be a simple anthology series, with the Watcher serving as the only common thread to link each episode together. But while each previous episode has had little-to-no connective tissue, the season finale embraces continuity, weaving several disparate plot threads together into a single epic conclusion. But as fun as it is watching T’Challa and Killmonger fighting on the same side, or seeing Peggy Carter share a drink with Thor and Doctor Strange, the Guardians of the Multiverse are only the beginning of this episode’s masterful use of continuity.

Soon, the showdown between the Guardians and Ultron begins, kicking off an epic clash reminiscent of the battle of Titan in Avengers: Infinity War. But while that fight was against Thanos with only four Infinity Stones, Ultron has all six at his disposal. So needless to say, it isn’t long before the heroes need to fall back. But before they do, Strange Supreme opens a portal to another universe — specifically, the zombie-infested Earth from Episode 5. As the heroes retreat, Ultron is swarmed by a legion of the undead: including the zombified Scarlet Witch, who manages to hold Ultron off long enough for the Guardians to make their escape.

The Guardians of the Multiverse escape to Ultron’s homeworld, where they encounter the final member of their team — the Black Widow from Episode 8, who joins forces with her fellow heroes to defeat the villain who ravaged her world. And after a long and intense battle, Ultron is ultimately defeated because of another plot point introduced in the previous episode. Namely, Hawkeye’s arrow that contained Arnim Zola’s AI, which he and Natasha used in their attempt to take down Ultron in Episode 8. Even the final battle for the fate of the multiverse is won thanks to the payoff of an already-established plot point.

Scarlet Witch prepares to fight Ultron in What If...? Episode 9

However, there’s still one last unexpected callback found in the episode’s conclusion. After all the other Guardians of the Multiverse have returned to their home universes, Natasha is left alone with the Watcher. She confronts him over his inaction while her world suffered, just like Ultron and Strange Supreme did before her. But as Uatu tells her, “You, your stories, they are everything to me.” So, as a last show of compassion, the Watcher grants Natasha a new home — a world without a Black Widow. That’s right, it’s the universe from Episode 3, where Nick Fury is fighting alongside Captain America and Captain Marvel against the forces of Loki. Not only is this scene a reference to a past episode, it also serves as the perfect conclusion to both the Watcher and Natasha’s character arcs.

That, more than anything, is what this episode gets right about continuity. Callbacks for their own sake can come off as stale, but Episode 9 references previous episodes solely for the sake of advancing the story. From the Guardians of the Multiverse teaming up to Strange Supreme unleashing the Marvel Zombies, from Zola’s virus defeating Ultron to Natasha finding her new home, every single returning element is the payoff to a setup from earlier in the season — everything serves a purpose. And because of that, the season finale of What If…? manages to turn a series of self-contained stories into a single interwoven narrative that provides closure for both its returning characters and the overarching plot of the season. Not bad for the MCU’s first attempt at an animated series.

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