I’ve noticed that in some asks about a pokemon’s behaviour, sometimes you recommend and in others you don’t bring this up at all and instead suggest allowing them to breed. Is this because certain pokemon cannot be neutered? Which ones?

Actually, I don’t often bring up the subject of breeding because not all behaviors have to do with sex, contrary to what Freud may have you believe.

Joking aside, whether or not it would be prudent to have a pokémon breed depends on completely on circumstances. If a pokémon is depressed, then companionship may be the best solution, as many pokémon are actually social in nature. However, aggression is a sign of unchecked sexual frustration, and sometimes, neutering can allow a pokémon to gain control of their temper by reducing their hormone levels to a manageable state. Likewise, if it’s clear that the owner doesn’t wish to raise young or if the pokémon wanders off to mate with a large amount of wild pokémon (or pokémon owned by other trainers), neutering may help to reduce a pokémon’s urges, which in turn will help control the population of unwanted hatchlings.

In other words, whether a pokémon should breed or should be neutered depends entirely on circumstances. In some cases, one is simply a far better option than another. Likewise, it’s also worth it to note that although I was largely kidding in my first line of this response, it’s true that not all instances of aggression or wandering have to do with a pokémon’s libido. Sometimes, they’re simply signs of stress, lack of sleep, or something far, far simpler than sexual frustration.