Life is stranger than fiction

Eyespot caterpillar the inspiration for a Pokémon character

Papilio troilus looks like the work of a cartoon animator, but instead this species was actually the inspiration  for a character called Caterpie from the cartoon Pokémon. Apparently, insects were used heavily as inspiration for Pokémon species.

Pokémon characters inspired by swallowtail butterflies. Left to right: Caterpie, Butterfree, and Metapod.

Late instar Papilio troilus in a leaf shelter [Photo: Wikipedia.org] 

Caterpie has several features similar to Papilio caterpillars including large eyespots, and a Y-shaped osmeterium - a defensive organ charateristic feature of the Papilio genus. It also has a green dorsal body and a yellow ventral side, and therefore most closely resembles larval Papilio troilus and the closely related Papilio palamedes. Either of these species could have been the inspiration for Caterpie.

Yet, various websites [wrongly] cite other Swallowtail species as the inspiration. For example, the current Wikipedia page lists Papilio cresphontes as the species on which Caterpie is based, but P. cresphontes isn't green during any of it's larval stages and doesn't even have eyespots (#TaxonomyFail)! Papilio glaucus is cited as the model here, which is a closer guess (at least this species is green with eyespots), but this is also wrong because P. glaucus lacks the yellow underbelly (instead it is a lighter green than the dorsal side).

Final instar Papilio thaos caterpillar which looks nearly identical to Papilio cresphontes which has been wrongly cited as the inspiration for Caterpie.

Final instar Papilio canadensis caterpillar with the osemeterium (a defensive organ) extended.  P. canadensis was considered a sub-species of P. glaucus until recently and both have very similar-looking caterpillars.

I have always thought the little downward-slanting markings within the eyespots of some Papilio caterpillars  (including Papilio canadensis pictured above) looked like the classic cartoon "eyebrows" used to indicate a character's anger (e.g. the Angry Birds logo). In fact, a similar technique has been used with Caterpie when the character is launching it's "String Shot" attack.

Caterpie launching the String Shot attack. Note the angry eyebrows. [Image from Bulbapedia.net]   

Just like real caterpillars, Caterpie eventually pupates into Metapod (which does resemble the chrysalis of Papilio species), and finally into Butterfree which does not look like any Swallowtail butterfly I have seen...