Genuine Curiosity: what happens when an egg breaks?
I get the slimy part, but how dangerous are the shell fragments?
I'm not a nurse or doctor, but I'd guess they're about as dangerous as anal play could get - which includes life-threatening. Shell fragments are strong and quite sharp in a body area not at all designed for physical protection. The cost of a cut inside you is the contents of your colon getting into your blood and abdominal cavity. And if you need to go to the hospital, you're probably getting surgery. Super yikes!
Medical articles, not about eggs specifically but about foreign bodies requiring medical attention, for anyone curious: Systematic review of rectal foreign bodies in older men: humanistic care and a novel challenge for society, Repeat presentation of large rectal foreign body requiring surgical intervention