Helen Bristol wrote to Don saying that shed recently bought a dozen eggs and about half of them were double yolkers. Helen wants to know how this happens, and if there are any beliefs surrounding eggs with double yolks.
Don explained that a double yolk egg is simply a set of twins. On occasions the twins hatch and survive, although it is very difficult for them to chip their way out of the egg. Young hens, called pullets, often produce double yolkers when they first start laying.
There is a belief that a double yolk egg indicates bad luck, but apparently the bad luck is cancelled out if you crush the shell.