King’s Rock
Politoed in depth
Nyorotono, lord of the tadpoles
The Japanese name, ニョロトノ, combines the “nyoro” that runs through the whole line from the first tadpole with “tono”, the title once used for a feudal lord. English does something else: Politoed combines polliwog, the tadpole, with toad. Both names point to the same thing by different routes — an amphibian that has risen in rank.
The item that triggers the evolution completes the joke. The King's Rock only makes two species evolve in the entire series, and both end up with crowns: Politoed and Slowking. The design does the rest with two visual cues: the upright stance, which breaks with that of its earlier forms, and the curl on its forehead, which the entries insist on treating as a badge of rank rather than hair.
Three generations waiting for rain
It arrived in Generation II, at number 186, as the alternate final evolution of a line that had only had one until then. For a long time, that was exactly what it was and little more: a decent Water-type Pokémon, with good Special Defense and no real argument of its own against the many Water-types that did the same thing.
Drizzle changed the script in Generation V, when it became available as a Hidden Ability. Summoning rain on entry turned a nondescript species into the piece holding an entire strategy together. At the time, the rain didn't expire: it lasted until another weather effect replaced it, and a single switch could tilt the whole match.
Generation VI scaled that back. From then on, weather summoned by an Ability lasts five turns, or eight if the Pokémon is holding a Damp Rock, and the plan went from permanent to a countdown. The practical consequence is that turns now have to be managed: bring it in at the right moment, not at the start out of habit, and know which teammates are going to make use of those five turns before the rain clears.
The little it learns on its own
It's worth looking at the level-up list, because it's ridiculously short. In Scarlet and Violet it only has four moves at level 1 — Tackle, Hydro Pump, Belly Drum and Rain Dance — plus Bounce as a remembered move. Everything else comes from TMs or is inherited from its earlier forms. That's the usual price of trade evolutions, although the figure stands out here.
There is one oddity in that list. Belly Drum sacrifices half its HP in exchange for maxing out Attack, and Politoed has 75 Attack, the worse half of its stat spread. The physical moves it could chain afterwards, Liquidation with 85 or Waterfall with 80, don't make up for the damage. It's a move it learns because that's how the list works, not because it helps.
Against Poliwrath, Poliwhirl's other branch, the roles are clear. That one is a Water and Fighting type that hits with its body; this one gives up the second type, stays pure Water and puts everything into the special side and its Ability. If you want to trade blows, you have the other one. If you want rain, this is the only option in the line.