[Pokemon] How exactly does Ditto's Copy ability actually work in the anime?

In the game, Ditto copies all the stats and abilities of the Pokemon it uses the Copy ability on. I'm wondering not only how he can do so (like if there's some kind of non-pvysical realm he pulls their essence from), but if there are limitations to the ability. If the opposing Pokemon is not in shape, will it transform into the same out-of-shape? If a Pokemon has trained for endurance all their life, will Ditto have that same endurance? If the opponent can hold their breath for a long time, can Ditto do the same because that specific Pokemon can do it?