I’m sure someone’s already talked about the callback to 13x16 ScoobyNatural in 15x14 Last Holiday, as well as to 14x15 Peace of Mind ?

@postmodernmulticoloredcloak  and @mittensmorgul  this is right up both your streets. 

First of all - look at the numerological correspondence, which the writers’ room played with significantly in episode call-backs last season (e.g. 14x14 Ouroboros and its deliberate correspondences to 4x14 Sex and Violence). 

15x14 Last Holiday is a mirror image of 14x15 Peace of Mind.

The ground-hog day style pseudo happy-world Mrs. Butters creates for the Winchesters, recalls the 1950s style supposed “paradise” Chip Harrington artificially kept his town trapped in. 

However, whilst Chip was an irredeemable control-freak (and a Chuck mirror), Mrs. Butters is a torture victim (of the Men of Letters) and she is eventually able to break free of her conditioning and let her “prisoners”, Sam, Dean and Jack go (and they return the favour by not “ganking” her, as they would have, once-upon-a-time). There’s redemption there. Whereas Chip’s daughter Sunny had to trap Chip inside his own mind, permanently, to stop him controlling others. 

In terms of the related correspondence with 13x16 ScoobyNatural, @mittensmorgul​ often tags Dabb’s Ouroboros (circular/ spiral structure) with  “Scheherazade“. Scheherazade is the storyteller in The Arabian Nights, whose stories so fascinate the murderous king, Shahryar, that he spares her life, over and over, to hear them, until he has fallen in love with her and revokes his threat.

ScoobyNatural is an Arabian Nights style story-within-a-story, because it is SPN in a cartoon world, in an AU mash-up with the Scooby-Doo gang. In the re-appearance, from that story, of Dean’s snuggly purple nightshirt, transferred/ re-imagined from the ScoobyNatural cartoon-world into the fairytale world of Mrs. Butters’ Last Holiday, the narrative structure of the WInchesters’ universe is revealed to be collapsing in on itself, bleeding into itself, as Chuck closes in on the ending he wants (a tragic Winchester brothers’ murder-suicide). 

There’s a parallel here, between Scheherazade as the Winchesters and Shahryar as Chuck. “Our” Sam and Dean are Chuck’s favourite story, so much so that, even amidst his current multiverse-destroying bender, he has already crushed other worlds and other versions (like the world the Sam Smith and Dean Smith a-like Winchesters come from in 15x13 Destiny’s Child), but, he has saved the ending of his favourite story for last. 

The question is, will Chuck have a Chip Harrington ending or a Mrs. Butters ending? Mrs. Butters also functions as a potential Chuck mirror.

And the story symmetry does suggest a Mrs. Butters ending - because the emotional growth on the earthly plane which the Winchesters are undergoing, as they learn how to be good fathers, despite their own shitty parenting by John, should, for reasons of narrative and alchemical symmetry, be mirrored on the cosmic plane, with Chuck also learning how not to be a shitty God/ writer, according to the logic of the Ouroboros/ alchemical story structure. And, as I’ve said before, Vonnegut-style, that growth points to Chuck letting his characters go at the end, the way the Winchesters and Mrs. Butters mutually agree to let one another go at the end of Last Holiday.