Just from the lame horse pun in the title, it's immediately obvious what "A Hearth's Warming Tail" will be. At the very least, it's a Christmas episode in May, which makes season 6 the second season in a row to have such an episode, after season 5's "Hearthbreakers." More specifically, the episode is an adaptation of Dickens's A Christmas Carol, and as that might suggest, this is a step away from the attempts at character development and nuance which defined the rest of the season. Although that might seem disappointing at first, however, "A Hearth's Warming Tail" boasts some of the how's purest delights in a while.
Although the story of A Christmas Carol by now needs no imtroduction, "A Hearth's Warming Tail" makes small but meaningful alterations. The episode is framed by Twilight Sparkle reading the pony-world equivalent of the original story in an attempt to convince her pupils of the merits of Hearth's Warming. Starlight holds the perspective that Hearth's Warming is just about the presents and candy, and although this is argument over the meaning of Christmas is fairly well-worn, it's neat to see natural discussions about pony customs.
In this iteration, Ebenezer Scrooge is replaced by Snowfall Frost, who is visually represented by Starlight in an attempt to thematically rhyme the story with the framing device. It's more successful here than it was in season 2's "Hearth's Warming Eve," primarily because the story here is already so well-known and because adapting it with familiar characters is itself very common. The story diverges from the source marial in three significant ways: first, Snowfall isn't met by a dead associate; second, she attempts to magically remove the holiday from existence; and third, her motivation is entirely different.
One of the biggest successes of "A Hearth's Warming Tale" is its acknowledgement of the show's world and mythology. Now that the story exists in a magical world, Snowfall's hatred of Christmas takes on a more tangible form, and the show is able to slightly raise the stakes while also altering the story. The spirits of Christmas past, present and future (represents by Applejack, Pinkie and Luna, respectively, in an inspired bit of casting) don't visit Snowfall in her sleep but are instead summoned by her attempt to stop Christmas. It's not a change that affects the message, but it does keep the story fresh.
Each spirit's vision is a bit dfferent, as well. The Spirit of Christmas Past has perhaps the most significant change, showing a simpler past for Snowfall: her magic instructor in school planted in her the idea that Hearth's Warming is frivolous, implanting in her an ethical code of working hard and seeking to improve Equestria. Much more than anyone in "No Second Prances," Snowfall's motivations are nuanced: working hard and striving to improve Equestria are worthwhile pursuits, but that doesn't mean they should come at the expense of friendship and merriment. The episode's biggest issue is its apparent dismissal of wanting to make the world better, but that's offset by how it reinforces the show's philosophy: That those who do wrong can become better. More significantly, Snowfall's motives parallel Starlight's, in that she's trying to help Equestria while doing exactly the opposite.
The spirit of Hearth's Warming Present takes her name under a different meaning, as in "presents" rather than "the present." She ultimately has the same effect as her counterpart in the original story, showing Starlight the joys of Hearth's Warming, specifically in this case how good it is to give. The initial lesson of teaching Scrooge not to be greedy is weakened by Snowfall's own ethos, as her desire are more intangible and arguably move, but her pursuits are early on demonstrated as isolated and self-focused. To Snowfall, Hearth's Warming is a distraction, and the ponies around her don't matter.
The spirit of Hearth's Warming Future, meanwhile, displays the biggest thematic change. The Windigo myth from "Hearth's Warming Eve" returns, and although both Snowfall and Starlight initially question its legitimacy, Snowfall is shown that if she stops Hearth's Warming, she will bring the Windigos back. Perhaps this exaggerates the holiday's importance to harmony among ponies, but then again, that's what Christmas stories are supposed to do. It's great to hear about the Windogos again, and the nuance of Snowfall's motivations is here reinforced. Her plan to stop Hearth's Warming is selfish, but she says one of her goals in life is to better Equestria. And yet, her plan for a better Equestria turns out to be worse for Equestria in reality, something Starlight no doubt sympathizes with.
As an adaptation of a known story, "A Hearth's Warming Carol" needs to be a showcase of pure quality in writing, animation, and music. Thankfully, on top of the clever narrative alterations, "A Hearth's Warming Tale" succeeds on a technical level as well. Every song is delightful, the visuals are gorgeous and never tarnished by a goofy facial expression, and the writing is top notch from start to finish. The result is a delightful adptation, and while it packs relatively little complexity of narrative momentum compared to previous episodes, there is some character development for Starlight, who comes to understand friendship a little more and bonds with the mane six through her eventual participation in the festivities.
With these interesting changes to the original story, some solid thematic resonance, and superb craftsmanship, "A Hearth's Warming Tail" might be the best episode of season 6 thus far despite being possibly its simplest. It's a familiar story, but the show provides a fresh, delightful take on it which blends the original story with the show's characters and setting. So yeah, it's a Christmas episode in May, but quality is quality at any point of the year.