The world of Pokémon might seem like a bright and cheery place, but underneath all this, there is a dangerous hazard that could have apocalyptic consequences. It's all thanks to one seemingly innocuous Pocket Monster: Ditto. Pokémon breeding is already a complicated matter, wherein the genetic diversity of the various Pokémon involved in the process results in the next generation of Pokémon becoming stronger from baby Pokémon inheriting IVs, TM and HM techniques, among other factors.
However, while Ditto might in theory provide an easy way for Pokémon to reproduce, Ditto also severely limits the genetic diversity of the Pokémon gene pool. As a result, there is a distinct possibility that should a group of sexually excited Ditto keep breeding with Pokémon, it might create a terrifying scenario that eradicates genetic diversity from the world of Pokémon. In other words, creating a planet of clones.
How Pokémon Breeding (Normally) Works, and How Ditto Changes Things
Pokémon breeding is a complicated matter. Much like in real life, biodiversity is spread by two separate Pokémon breeding with one another, passing on certain genetic traits to their child. Only Pokémon in the same Egg Group can breed with one another. This is except for Ditto, who can breed with any Pokémon, even genderless ones who normally cannot breed. However, by choosing to breed a Pokémon with Ditto, you miss out on potentially altering the future of your Pokémon's genetic mix, resulting in a Pokémon that is functionally either a clone of their parent or even less powerful than their parent.
If one Pokémon holds a certain item, it might result in a Baby Evolution being born instead of a Base Form, such as when Sudowoodo holds a Rock Incense, resulting in a Bonsly. Pokémon bred in certain regions might result in physical differences. When a non-Galar Ponyta breeds in Galar, they will give birth to a Galar Ponyta -- unless they're holding an Everstone.
However, the most distinct way Pokémon breeding stands apart is in how Baby Pokémon inherit abilities, IVs, moves, and other features from their parents. Female Pokémon have an 80 percent chance of passing on their Hidden Ability to their baby. By contrast, male Pokémon breeding with a Ditto only has a 60 percent chance. But if they breed with a female Pokémon, they have zero chance of passing it down. Baby Pokémon can also learn up to three IVs from their parents -- or five if one parent holds a Destiny Knot.
Baby Pokémon can inherit their parents' moves, too, whether it's a move learned by leveling up, TMs, HMs, or moves taught by the Move Tutor. However, these options are greatly diminished if a Pokémon breeds with a Ditto since Ditto can only learn one move: transform. And that move can only be learned by two Pokémon: Ditto and Mew. If both parents know a move via leveling up, for example, that baby will definitely learn that move whereas in earlier generations, this was only the case if the father knew a TM or HM move, and only then, there was only a chance the baby would learn it. The only way a baby can inherit a move from its parent when breeding with Ditto is if the other Pokémon is genderless.
Ditto Breeding Results in Bland Clones of The Parent, Which Presents Problems
As previously mentioned, Ditto breeding with gendered Pokémon results in less biodiversity. Most often, it's comparable to Pokémon cloning, with very few new or unique features being added, such as Hidden Abilities or new moves. Ditto can only do this, of course, because it can transform into any Pokémon. However, when transforming, Ditto gains the other Pokémon's type, moves, stats (other than HP), and even physical features. This means, essentially, that any Pokémon breeding with a Ditto is breeding with a genetic copy of itself.
What's bad about less biodiversity in the Pokémon world is that it would become a place filled with offspring that essentially inherit moves and stats that are shared by every other Pokémon -- with a lower probability of inheriting Hidden Abilities and other TM moves, too. In a hypothetical extreme, this means that an entire species can breed with Dittos, resulting in every new Pokémon in a species being a clone of the parent.
This might result in an awful scenario wherein genetic diversity, IVs, and any other factors that make individual Pokémon unique become phased out. Over a long enough period of time, Pokémon would become near-identical clones of one another, breeding with Pokémon that are functionally themselves or with Ditto that continue to transform into alternate gendered clones of one another.
It would result in a world where the Genderless Egg Group would become every Egg Group -- or, at least, they would functionally, given the identical nature of every Pokémon in a species dominated by Ditto breeding. While it's an unlikely extreme-case scenario, the world of Pokémon should fear Ditto and its desire to breed with everything.
