Two lepers meet on the street.
First says "How are you doing?"
Second says "Mustn't crumble!"
Mustn't Crumble
Explanation
Explain Bear
Listen up, buttercup. This joke is dark, like your soul, probably. Leprosy is a disease that makes your body parts fall off. One leper tells the other not to 'crumble' because, you know, they might literally crumble and fall apart. Get it? Probably not.