On the Origin of Species: Slowpoke, Slowbro and Slowking
How about the Slowpoke family?
Stay with me here. Slowpoke does indeed resemble a stylized pink hippopotamus. It's Slowpoke's evolutions – Slowbro and Slowking – where the snail association emerges. That peculiar creature that becomes attached to Slowpoke to trigger its evolution is repeatedly said to be a Shellder, though it bears little resemblance to one. Shellder, like Cloyster and Clamperl, is based on a bivalve. The shell that latches on to Slowbro and Slowking is based on that of Turbo cornutus. Also known as the horned turban, T. cornutus is a marine snail found mostly in Southeast Asia. It's considered a delicacy in Japan, where it's known as sazae (栄螺), and is recognizable by its distinctive spiky spiral shell.youkai. In this case, it's the sazae-oni (栄螺鬼) or turban shell demon. The story's earliest origins are unclear, but the first written record of the creature is in the works of eighteenth-century writer and illustrator Toriyama Sekien. Indeed, it's likely he actually created the sazae-oni, though some variants of its story are likely derived from earlier local myths. His illustration shows a monster with a roughly human-like torso and arms, but with the lower body emerging from a large turban shell and the replaced with another shell, complete with eyes. More modern depictions usually include just one shell: the lower-body shell seems a slightly more common choice than the head shell, but depictions of both versions are plentiful. Variants of the sazae-oni show up in a lot of Japanese media; it really seems to be a youkai that's captured a lot of creators' imaginations.
Of course, every youkai needs an associated story, and the sazae-oni has a few different legends attached. One such story is that is that a sazae that lives for thirty years can become a sazae-oni, similar to the stories of tsukumogami, inanimate objects that come alive upon reaching a certain age. The sazae-oni of this tale are quite peaceful and harmless despite their bizarre appearance, emerging from the sea only to dance in the waves at night.
The other common story about sazae-oni is altogether less wholesome. This version of the creature is the result of a lustful woman being cast into the sea, causing her to become something not unlike the succubus of western folklore. Though in the kind of twist I've come to expect from Japanese folklore, the sazae-oni succubus steals the testicles of the men she seduces. One tale describes a ship full of alarmed pirates discovering the attractive lady they pulled from the sea has robbed them of more than just their dignity, and subsequently bargaining to buy back their purloined parts. The point of this story seems to have been a particularly groan-worthy Japanese pun, as a slang term for testicles is kintama (金玉), meaning 'golden balls', so the pirates traded one kind of gold for another.
While the Slowpoke family aren't true sazae-oni (they're not really graceful enough for dancing, and I'm relieved to say there's no evidence of them doing any of that... other stuff), the influence of the myth on both Slowbro and Slowking is pretty clear: they represent the shell-on-lower-body and shell-on-head forms of the creature. In fact, I get the impression that the sazae-oni is such a commonly-seen creature in Japanese media that it's lost many of the associations with its (already admittedly nebulous) origins. And in the case of the Slowpoke family, I think that's probably no bad thing...