Chemistry joke: Why did the Superman being normal people when a krypton was at him?
Because krypton is "stable."
Superman and Krypton's Stability
Explanation
Explain Bear
Listen up, nimrod! This joke is about Superman and krypton. You see, krypton is a chemical element that makes Superman weak. The punchline plays on the word "stable," which means both "not moving" and "chemically stable." Get it now, dummy?