Warning: Game of Thrones season 8 episode 3 spoilers.
Where did she come from? How did she sneak past the White Walkers? To some it seems a bit Arya-ex-machina, with the young Stark's Hail Mary leap of faith coming out of nowhere and not really making sense. However, there's a small detail from the episode that adds an essential piece to the puzzle.
Before Arya lunges at the Night King, we see Jon Snow trying to make his way into the godswood, where Bran Stark and the Night King are. The path is blocked by Viserion, the White Walker dragon. Jon tries to run past him, but he's spotted by the dragon. Jon ends up trapped behind the battered remnants of a wall and decides, with nowhere left to run, to confront Viserion. Except he doesn't raise his sword, he just stands up and yells.
Here's what you may have missed: Jon yells "Go!" One long one and then another short one. In the very next scene we see one of the White Walker's hair flicker in wind -- wind created by Arya as she makes her way to the Night King.
In other words, Jon saw Arya and distracted the dragon so that she could make her way through.
Not only would this make sense in terms of clearing a path for Arya, it would also absolve him from the stupidity of trying to kill a dragon by yelling at it.
It looks like we're not the only ones to notice this. After writing it was brought to our attention that a similar argument was made in this Reddit thread. In the theory's wake i09 made the (pretty fair) argument the theory is sexist as it removes some agency from Arya's Night King kill. Our take: it doesn't take anything away from how awesome Arya is, just makes Jon's decision to shout at a dragon less idiotic.
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Foreshadowed: In episode 1 of this season, Jon is standing by the weirwood tree, exactly where the Night King looks down on Bran. He turns around to find Arya has crept up on him without him noticing. The show's creators were giving us a last-minute reminder about her stealth skills. Similarly, during a light duel with Brienne (that's Ser Brienne to you) in season 7, Arya bested Brienne by flicking her dagger from one hand to the other, just like how she dropped the same dagger from one hand to the other before ending The Long Night.
Leaving as he enters: Back in season six, we see the Children of the Forest create the Night King by pinning him to a weirwood tree and plunging a dragonglass dagger into his heart. The weirwood tree could be the key to the Night King's vulnerability. After all, he sure did seem indestructible when he was being assaulted by dragonfire. If not, it's at least some nifty circularity.
See a Ghost: Ghost, Jon's direwolf, reappeared in episode 2 of season 8 after a noted absence from the spotlight. He was then seen at the Battle of Winterfell, charging into the wights alongside the Dothraki and Ser Jorah Mormont. Jorah came back, but most of the Dothraki didn't. Ghost wasn't seen for the rest of the episode either. But don't fret, direwolf lovers, he was spotted.
Thread the needle: Arya got her first sword, needle, from Jon back in season 1. "First lesson," he told her, "stick 'em with the pointy end." That's the same advice Arya gave Sansa when she sent Sansa down to the crypts with her dagger as the army of the dead approached. Of course, Syrio Forel, Arya's first official stabmeister, was referenced later by Lady Melisandre. "What do we say to the God of death?"
Brown eyes, blue eyes, green eyes: One of the most important callbacks made in the episode was in reference to the first meeting of Arya and Lady Melisandre. All those years ago, The Red Woman prophesized that Arya would permanently shut brown eyes, green eyes and blue eyes. Those blue eyes turned out to the Night King's. Now some fans are speculating the green eyes could be Cersei's.
A dagger's journey: The dagger Arya plunged into the Night King saved Bran, and everyone else. Seven seasons ago, though, it was meant to kill Bran, as an assassin was armed with it after Bran saw Jaime and Cersei, uh, exploring their sibling bond. The dagger belonged to Petyr "Littlefinger" Baelish, who also used it to betray Ned Stark. Littlefinger gave it to Bran last season, and Bran gave it to Arya.
Hopefully we'll get a decent explanation next week on exactly how Arya traveled from the room with The Hound and Lady Melisandre to the godswood.
Originally published May 1.
Update, May 2: Adds extra details, Twitter reactions.
Update, May 3: Adds links to others positing the same theory, and reactions to the theory.