okay, just putting this all together for ease of access, since it's been spread out across several posts now--
The day after it aired I watched the ending like actually 30 times and I became fully 99.999999% certain they switched places. I was initially thinking during the kiss, cuz of how the camera angle changes, but after watching an additional 20 times a few days later, I'm personally leaning much more towards them stopping time in the instance after "no nightingales".
Before the kiss, Aziraphale is saying "nice" things about the Metatron, but his face and voice keep switching to broadcasting distress, and they make it a point to show in ep 1 that Crowley can read him just from tone of voice
As they're pulling away after the kiss, they lock eyes and "Aziraphale's" expression shifts in the teeniest tiniest way, like a confirmation glance, before they shift back (and Michael Sheen is a master, so no chance it's not on purpose)
---(Like really, go back and watch how Aziraphale's expression shifts literally *a second* before "I forgive you" cuz the change is SO minute, but entirely different emotionally.)
Also the way he moves his jaw right after he pulls his hand away from his lips, is a bit from MS's Crowley (you can see it in the very last two seconds of this vid- link)
Aziraphale's hands -stay by his sides- after that, he doesn't clasp them at all, and it's particularly noticeable while he's walking to the elevator with Metatron. The way he walks is very stiff and precise, similar to after the swap in S1.
We don't see the underside of Crowley's jacket collar after the kiss, at any point (it is for sure red at the beginning of the ep, you can see it right before he changes in Heaven)
The Bentley drives away SLOWLY, which is how Aziraphale drives, and we're specifically shown that it only plays other music for Aziraphale
the seats in the Bentley are black as it drives away. They're usually brown, and the only other time they're shown to be black is when Aziraphale drives (@picturesque-about-it broke down the times so you can see-link)
---extra pic for anyone saying it's "cuz Aziraphale is lighter"-- the seats are still brown behind Crowley when he wears white
there's people wearing yellow in -every- part of the scene showing the Bentley both before and while it drives away! (link for pics/credit)
Aziraphale's smile in the elevator looks more like MS's Crowley. It's very similar to the trial during S1, but also (link)
This also explains why they're on opposite sides than they're usually shown while the end credits roll
many good points made by other folks here, about cues and snakes in beehives and swap motifs throughout the season-- link
The clock! Someone mentioned how the scene is so quiet you can hear it ticking, so I watched the ending a further 50 times to double check----I need to preface this by stating, I don't think this is a working clock, mainly cuz the hands aren't 100% where they should be between the minutes and the hours, like -a person- moved them to that time manually
When they're talking, the clock is at approximately 9:25 (?, again the hour hand isn't precisely set), then they walk across the room, and kiss, and immediately after that the clock is set about 15-ish minutes later (link to timestamps)
thanks to these bts shots, we can see that the clock on the opposite side of the room registers the SAME time difference before and after the kiss (link)
the first time Aziraphale looks "towards the window", I'm petty sure he actually looks further back towards the clock, *focuses on it* as Metatron walks up to him, and then spends the ENTIRE REST OF THE EXCHANGE blocking the Metatron's view of the clock
we're shown earlier in the season that Crowley can localize his time-stopping to a certain extent, like when he stopped the doctor and the rest of the room kept going, so it is possible he only stopped everything -outside- of the bookshop
---I KNOW Neil said it's a continuity error, but he also fully said "No" about there being a season 2 just days before they announced it was already written and in production, so. Take him at his word if that's what you wanna do.
---also I DID go back and look it over, and the clock IS consistently specifically set the entire rest of the episode as far as I can see. From the shots when you have a clear view of the clock, the angels and demons enter the shop at around 6, Maggie and Nina leave at around 7, the Metatron comes in at 8-ish, Aziraphale comes back in at that approximately 9:25
(insight from someone who works in production- link)
the music right before the kiss scene is the same leitmotif (Life After Death) used when they originally started formulating the swap in season 1! (link)
the movie Stairway to Heaven (1946) is featured as a poster in both the opening credits and in Maggie's shop (link)
the climax of the film has one of the leads willing to "take the place" of the other in heaven
(they also used a time-stopping mechanic, and the chess book Gabriel tests gravity with also plays a key role in the film)
and one last mention, extra food for thought--- the season's focus on their trusting one another, their history of performing "death (and heaven/hell) defying" feats together, and how they always get the trick right when it truly counts the most
that's what I've got so far!
If I'm right, they're apart now, but are actually more together then ever, and I find that terribly exciting. (And if I'm wrong, that's okay too! I'm just here to have fun.)
I'm not particularly concerned with very specific reasoning (that's for season 3 to tell us!), but I do think this theory is extra fun cuz pretty much any of the others could be the "why" driving it.
I'm not trying to convince anyone, or put down any of the other theories, so if you're not feeling it, that's okay! I'm just sharing what clues I'm seeing, so you can check if you see them too. 💕
