Big Cheetahs

Listen up, buttercup. This joke is playing on the term "big cat." Usually, it refers to, like, lions and tigers, you know, the large feline predators. But here, the joke says cheetahs are big cats because they "poo" (you know, take a dump) and "purr." See, it's twisting the meaning, which is kinda funny if you're not a complete airhead, which you are.