X2! Another good reason to get it a buddy is because if the duckling is male it will turn into a real monster once it reaches sexual maturity. It will try to mate with people, and might even attack other people. I have seen this in my own ducks, peafowl, and chickens, and there have been many...
I've seen a shelled egg followed by a shell-less egg, and several people have reported three shell-less in less than 24 hours, but this is the first time I have heard of two shelled eggs.