Forretress in depth
A riveted bagworm
The design comes from the bagworm, the larva that makes itself a case from whatever it finds around it and hangs from a branch inside it. The entire line comes from there. Pineco imitates the plant-based case, the one that looks like a pine cone; the evolution replaces that material with sheet metal. It is the same creature solving the same problem with better materials.
The English name combines fortress and forest: the fortress and the forest, which is exactly the bug in summary form. The Japanese フォレトス (Foretos) builds the same thing from the same two pieces, which does not always happen—many species change their joke when they cross the Pacific, and this one does not.
The strangest detail in the entry is that the official category is still Larva Pokémon after it evolves. The Pokédex describes a 125-kilogram sphere of metal and then classifies it as an immature insect. It is never explained whether that means there is something else at the end of the metamorphosis.
From Johto to Paldea
It debuted in Gold and Silver alongside the Steel type, which was introduced in that generation specifically to add new resistances to a game dominated by Psychic. Its repertoire was short even then, and already included Spikes, the move that has kept it a place on teams for twenty-five years.
What arrived afterwards changed it more than any stat tweak. Toxic Spikes appeared in Generation IV, in Diamond and Pearl, giving it a second hazard that poisons instead of dealing damage. Volt Switch arrived in Generation V, with Black and White, and let it leave the position while leaving damage behind. Sturdy, which in the early generations was limited to blocking one-hit KO moves, also began preventing any one-hit knockout with full HP in Generation V, and that is where the ability stopped being a footnote and became the basis of its plan. Overcoat, the hidden ability that negates hail and sandstorm damage, arrived later still.
Being the other Bug/Steel type
It shares its typing exactly with Scizor, and they have nothing else in common. Scizor points its best numbers towards physical Attack and reaction speed; here everything goes into Defense, and the corresponding 140 is one of the highest values seen in Generation II. They are opposite readings of the same type pairing: a resistance that hits and a resistance that stays still setting hazards.
The historical problem is that its job can be outsourced. Any species that sets Spikes, resists the same things and also has recovery can do its work with less risk, and the arrival of rivals with that profile in later generations gradually took space away from it. What it keeps exclusively is the combination of Sturdy and Explosion: it is guaranteed to survive the first hit, leaves the hazards in place and takes whatever is in front of it with it on the following turn.
How to use it in a normal playthrough
In story mode it works better than its numbers suggest, because the forest where Pineco appears is usually early in the adventure and level 31 comes soon. Ten resistances mean it can be sent in against almost any Trainer without fear, unless the opponent is carrying Fire.
Rapid Spin, at level 17, serves both to deal damage and to clear away the opponent's Spikes from its own side. Curse, at 23, raises Attack and Defense at the cost of Speed, the stat it cares least about losing. And Iron Defense, at 42, doubles the 140 to values where physical attacks stop making much of a dent. The full sequence—Curse, Iron Defense, Gyro Ball—takes too long for a battle against another human Trainer, but against a Gym's AI it works without breaking a sweat.