Hypno in depth
The dream eater and its silver ring
The whole line comes from the baku, the Japanese mythological being asked to devour nightmares. The Pokédex says it plainly about Drowzee: it descends from that legendary beast. The transition to Hypno is the interesting part, because the tapir stands upright, loses its striped belly and gains a mane and a pendulum — a flat silver ring that it polishes while looking for prey. It stops being an animal and becomes a professional.
The names follow the same path in both languages, although with a different tone. In Japanese it is スリーパー, “Sleeper”, the one that sleeps or makes others sleep, a direct continuation of スリープ, the “Sleep” of the previous form. In English, they went with Hypno, cut down from hypnosis, over the “Drowzee” that plays with drowsy. Japanese describes the result; English, the method.
What the second generation did to it
In Red and Blue, Special Attack and Special Defense did not exist separately: a single figure was used both to attack and to take hits, and in its case that figure was 115. With it, Hypno hit hard and took hits well at the same time, in a generation where the Psychic type barely had anyone to stop it.
The second generation split that stat in two and gave it the 115 on the defensive side, leaving the offensive side at 73. It lost the good half of its old profile. In the same batch of changes, the Dark type appeared, ignoring Psychic attacks and hitting its weak point. Two blows in a row against the same Pokémon.
Its Abilities arrived later and in stages: Insomnia first, Forewarn from the fourth generation onwards, and Inner Focus as a Hidden Ability further down the line. None of the three gave it its Attack back.
Compared with Kanto’s other Psychic type
Alakazam is from the same generation and the same type, and it is the exact opposite: where one puts Speed and Special Attack, the other puts HP and special bulk. A team that already carries a Psychic attacker does not need this one; what such a team lacks is someone who can take hits, and that is where 85 HP with 115 Special Defense actually says something. The problem is that its 70 Defense leaves it lopsided: any physical Bug- or Dark-type hit takes it out before its good defensive figures get a chance to matter.
The rest of its movepool fits wherever it can. Switcheroo, from level 1, and Trick, through a TM, swap items with the opponent, and with a burden in hand they are a legitimate resource against anyone who depends on theirs. Trick Room reverses the Speed order, but 67 is not low enough to get everything out of it. And there is a catch with Rest: Insomnia prevents it from falling asleep, including deliberately, so the Ability that protects it from the status also takes away the only decent recovery move it learns through a TM. With Forewarn or Inner Focus, the Rest and Sleep Talk combo becomes available again.