I have an overabundance of eggs right now, so I decided to hard boil some of the older ones. I noticed one egg that I didn't recognize - I only have 5 girls and I can tell their eggs apart. My parents have my chickens right now, so I didn't collect the egg from the nest. Anyway, it was a little bigger than a banty egg and round. When I filled the pan with water it floated. I took it out and cracked it open out of curiosity and was surprised to see a deformed yolk. It doesn't smell rotten. I looked up fart eggs, and couldn't find anything on unusual yolks, just that they seem to not have them frequently. Thoughts on what caused this? It seems to have been a one time fluke, but I'm interested as to possible causes.