Deer were one of the more obvious mammals that the first generation didn’t cover, so much like Spinarak, Stantler was inevitable.
That said, he’s very much on Seel’s level as “so close to a real-world animal they didn’t even change its pelt color”. He does have a few embellishments, like a ridiculously-round tail and a droopy, jowl-y face, but on the whole, if you asked a student to draw you a deer (or a caribou), this is roughly what you’d get.
The exception here is clearly the antlers, which do have a fun bit of automimicry going on. Giant eyeballs, and not placed to distract, but to give the illusion that the head is much larger than it is. I don’t know that it’s particularly effective, but hey – he’s trying.
Stantler is a plain normal-type with around-or-below-average stats, no evolutions, and not much of a niche to fill. He learns a lot of very diverse moves, sure; but he’s not especially great at using any of them, and he’s only even been available as a post-credits curiosity outside of his native Johto. There’s just not a lot of reason to use Stantler in the main games, I’m afraid.
So everything from this monster’s epithet “the Big Horn” to its anime appearances revolve around its horns. Big, illusion-generating organs that supposedly “bend air” to trick onlookers in the same way that heat mirages work – or even how proposed “invisibility” technology would work by bending light.
A more mundane explanation would be a combination of their size, shape, and odor. Those “balls” centered in his antlers are something of a natural medicine, used as a sleep aid but particularly notable for their bewildering odor. It even pairs up with the assertion that you’ll “feel quite strange” and “be unable to stand” by staring at them too hard, which is the G-rated pink-elephants version of a trip if I’ve ever heard it.
But the visual of a giant pair of eyes staring at you from the forest, giving you hallucinations? That’s some grade-A spooky-bedtime-story material. Great way of making a cartoon stag match the intimidation factor of a real animal of its size. Fun reversal-of-expectations But if supernatural power is the crux of his identity… why isn’t Stantler a Psychic monster, or possibly even a Ghost? Though I appreciate the notion of even a Normal-type having that sort of inner power.
Of course, this also means that female Stantler have full antlers by necessity, which is an especially nitpicky thing knowing that the series didn’t touch sexual dimorphism until seven years after Stantler first showed up. It’s kind of retroactively made Stantler a little weird, though, since his whole core concept only works if you ignore the notion of a “female stag”. Why was this monster not just made male-only again?
Okay, so the antlers are a mixed example. But he does have some redeeming factors – let’s go over them to cheer our deer-boy up!
His location! Johto was pretty plainly based on Kansai in Japan, which among other cultural centers contains the city of Nara. This city in particular has a reputation for the Sika deer population being remarkably tame, making them something of an attraction. And where do you think Stantler is found? Yup, right outside Violet City, the Pokémon town based on the real Nara. The designers love weaving more recognizable landmarks into the series’ maps, but it’s delightful to see them doing it with the region’s ecology.
His name! Odoshishi is pretty obviously a play on shishi-odoshi, those bamboo deer-scaring devices found in some Japanese front yards. In his way, Stantler works as a full-animal pun on this, because rather than a deer scare, you shuffle the syllables around and he becomes a scary deer who gives you night-terrors. Excellent.
Unfortunately, Stantler still has the basic problem of being a bit plain. We’ll eventually see a different monster give us a more unique take on the creature, and I kind of wish we could just roll Stantler’s more redeeming factors into that second pass at a “deer Pokémon” – or even an evolution to push him into “terrifying giant moose” territory. As it is, though, he’s not a strong-enough design to justify keeping around when we’re bursting at the seams with 900 critters already. I personally don’t mind him at all, but he’s objectively a design the series could Retire and not be too much worse off for it.