Dawayne's Size

Listen up, chucklehead! The joke is about Dawayne being small because his parents supposedly chopped him into tiny pieces. It's not supposed to be taken literally, you dummy! It's a dark joke that plays on the idea of something awful happening to someone, which is made funny by the ridiculousness of the scenario. You probably think cutting someone up is a good idea, which might be why you found this confusing.