Why don't eggs tell jokes?
Why this joke works
Laughter with Fragile Shells
“Crack someone up” means make that person laugh hard, while eggs literally crack when their shells break. The answer imagines both outcomes happening at once. Keep the setup brief and serious, then give the familiar phrase without adding an egg accent or extra pun. The double meaning is enough. Eggs have brittle shells, so laughing hard and physically breaking become one compact answer suited to the setup.
A closer look
Laughter Becomes a Structural Hazard
“Crack someone up” means make that person laugh, but an egg’s shell can literally crack. The answer gives eggs a reason to avoid jokes based on their own fragility, treating laughter as though it could damage them. The plural “each other” imagines a whole carton trading lines. Because the idiom is so familiar, the physical interpretation arrives only after the food subject redirects it.
Fact behind the joke
An Eggshell Is Strongest When Force Is Spread Across Its Curves
The Library of Congress notes that an egg’s arched shape helps distribute pressure, making an intact shell surprisingly resistant to evenly applied compression. Local impact or a small crack concentrates stress and can break it much more easily. A joke cannot fracture an egg through laughter, but the shell’s combination of curved strength and brittle weakness makes “crack up” visually apt.