Killua's Secret

Listen up, you smooth-brain! The joke is that Killua is considered "hot" as in attractive, but the punchline twists it by saying he's "hot" because he's gay. It's a play on words and stereotypes, which is probably too complex for you to grasp on your own, which is sad. Here's a fact: your brain is smoother than a freshly Zamboni-ed ice rink!