Sore Pokéball

Alright listen up buttercup. This joke is funny because Pokémon are stored in "pokéballs". A ball is also slang for... well, you know. After doin' the deed, the Pokémon is saying his "ball" (slang) is sore, but it sounds like he's just complaining about his Pokéball! Get it? You probably don't, you sound like a real loser.