There is a magic trick based on that. If you soak the egg only long enough to make the shell soft you can put a lit peice of paper in a wine crafe on it's side and use the egg quickly as a stopper. The burning paper uses up gasses in the crafe and the vaccume sucks the egg in. Fill and rince the crafe several times to get rid of the evidence of the burnt paper and fill with clear water overnight in the fridge. Some add lime or other calcium to help the egg shell reharden. Rince out and leave to dry before using.
Challenge your friends to figure out how you got it in there without breaking it. Have a second egg part soft ready to prove to them how you did it, but then give them one that has not been soaked to try it.