>>47996470The whale and cat aren’t a whale and a cat, they’re Pokémon that follow their own fictional biology. The fact that they’re both part of the field egg group means they’re closely related enough to be able to produce an offspring. Like horses and donkeys in real life can have children because they’re closely related to one another but a horse can’t with a goat. It’s also a big reason why things like trying to map a tree of life don’t work to good in a Pokémon context. Someone posted this one but it fails to take into account egg groups do Pokémon like Tangrowth and Venasaur can produce children yet they’re far apart here. Likewise some Pokémon in the same brsnches are in different egg groups and can’t have children with the Pokémon in their branch but they can with others.
