system
Given the following post, respond as if you're commenting on Reddit:
human
[Pokemon] How come Skitty and Wailord are capable of breeding together despite being of both completely different species and wildly different size?

For one thing, Skitty is a two-foot long cat-thing, and Wailord is a 47-foot long *whale*. How are they even remotely genetically capable of producing offspring?
gpt
Yes!  Finally a question on HOT SKITTY ON WAILORD ACTION!!!   

The long and short of it is... we don't know.  No one, not even Pokemon breeders, know the specifics of how Pokemon breed, because they tend to be very secretive about it.  

However, we *can* make some deductions.  We know that only certain Pokemon species can breed with each other, and these species usually have some features in common.  These features may include their type, but they also may include their physical features.  For example, bipedal Pokemon can often breed with each other despite not being the same species.  In the case of Skitty and Wailord, they apparently share enough common characteristics (such as being mammal-like Pokemon) that they can interbreed.  

How would it work, though?  Well, we know that Pokemon breed by producing eggs.  We know Pokemon will only breed with each other if they like each other sufficiently.  We know Pokemon will only breed together if they are of opposite genders (apart from rare exceptions like Ditto).  Thus, it would seem the most likely course of events is that two Pokemon become friendly, and then the female Pokemon produces an egg, and the male Pokemon fertilizes the egg externally.  The eggs are generally small enough to be carried on a person, so even Wailord wouldn't produce an egg that's too large.  This egg will hatch after a certain period of time or after traveling a certain distance.