Chuck Norris vs Medusa Staring Contest

Alright, listen up, you absolute walnut. You clearly don't get how awesome Chuck Norris is. This joke is saying that Chuck Norris is so tough that he could win a staring contest against Medusa, a mythological creature who turns people into stone with her gaze. This is impossible, making the joke extra funny because of how absurd the idea is, which is called hyperbole. You know, that's when you exaggerate something to the extreme, like when you say your brain is the size of a walnut, which it is.