Wurmple

A caterpillar, and one that knows how to defend itself. The two species usually cited as references are the larva of Cerura vinula, which raises the rear part of its body when disturbed, and that of the swallowtail Battus philenor, covered in fleshy tubercles. That is where Wurmple’s red spines come from, the ones it has on its back and tail. They are not decoration: Pokédex entries insist that it points them at its enemy and injects poison.

The rest of its behaviour is standard larva fare. It eats leaves. It scrapes tree trunks with the spines on its back until it removes the bark, then drinks the sap that comes out. It has suction cups on the ends of its feet, letting it cling even to glass without slipping, and it lives in forests and tall grass. It is prey, too: the Pokédex identifies it as Swellow’s preferred food and describes a Starly attacking one.

It is 30 centimetres tall and weighs 3.6 kilograms, its official category is the Worm Pokémon, and its role in the evolutionary line is that of a door with two exits. No other species does what it does when it evolves: split into two branches without the Trainer being able to choose or predict which one they will get.

195 base stat points, distributed in the worst way possible. Its highest figure is a tie of 45 in HP and Attack; then come 35 Defense, 30 Special Defense, and two bare 20s in Special Attack and Speed. Move the last one around and that is basically the definition of its stat spread.

Its regular Ability, Shield Dust, nullifies the additional effect of the move that hits it: no added burns, paralysis or flinches, although the damage still goes through. It is the only useful thing it gets out of the box. Its Hidden Ability, Run Away, lets it escape from every wild Pokémon, which is useless outside the wilderness.

Its pure Bug typing hits Psychic, Dark and Grass well, and runs into Fire, Flying, Poison, Ghost, Steel and Fairy. Defensively, it resists Fighting, Ground and Grass in exchange for three well-spread weaknesses: Fire, Flying and Rock.

And its movepool consists of two moves. Poison Sting, with 15 power, from level 1, and Tackle, with 40, at level 6. No TMs, no Move Tutor moves, and nothing from the Egg. There is no competitive discussion to be had here: it exists to last six levels, give up its HP EV point and disappear inside a cocoon. Its real place is at the start of a Hoenn playthrough, against Bug Catchers and in the tall grass on the first routes, where 40 power is still worth something.

Bug Egg Group, and only that one, with a 50% gender ratio, so breeding it is as simple as putting two together and waiting. Its 15 Egg cycles work out at roughly 4080 steps, among the shortest there are. It has no Egg moves, and it does not need any: the two moves it learns by level are already in place before level 7.

And level 7 is the entire evolution condition. At that point it becomes Silcoon or Cascoon, with no items, no time of day, no friendship and nothing else the player can control. It is decided by a hidden value set when the specimen appears in the wild or hatches from an Egg. Ten levels later, the butterfly or moth arrives.

In the wild, it appears in forests, and its catch rate is 255, the maximum: throw a Poké Ball at half health and it is already inside. It can be holding a Pecha Berry or Bright Powder, two items worth more than the Pokémon itself. It grows at a medium rate and gives 56 base experience when defeated, the kind of figure you would expect from a creature caught to fill out the Pokédex.