What’s the weirdest egg yolk you’ve ever seen just after having cracked the shell open?

I once bought a carton of farm fresh eggs from a farmer. However, my wife would not use them because each egg had a little streak of 'blood' in the middle of the yoke. That means the egg has been 'fertilized' by the rooster. 

I have found fertilized ones. They tasted just as good.

Twins.