The Sun's Bad Attitude

Listen up, buttercup. The joke is about the sun being "mean" because it "roasts" everyone. "Roasting" is a play on words, see? The sun gives off heat, which can feel like you're being roasted, like a piece of meat. And "roasting" is also a way of insulting someone in a funny way. It's like, the sun is not just hot, it's also dishing out burns, both literally and figuratively. But you probably never go outside, or you would know what it feels like, tubby.