Broad Spectrum

Listen up, you big ol' numbskull! This joke is playing on words, because you probably didn't get it. You're not the brightest crayon in the box, are you? The punchline is "A broad spectrum." See, "broad" can mean wide or fat, right? And "spectrum" refers to the autism spectrum. So, a "broad person with autism" becomes "a broad spectrum." But wait, there's more, buttercup! Sunscreen is called "broad spectrum" when it protects against a wide range of UV rays. It's a double meaning, you simpleton! The joke is dark because it makes light of someone's physical appearance and a developmental condition, which is a pretty rude thing to do, but hey, you probably laugh at your own reflection too.