Eggs With Double Yolks ! What If ?

Say you were to take a DOUBLE YOLK EGG and before processing the thing for the Supermarket Shelves you incubate it under a Hen or other means and Hatch it would you come up with what? A 2 headed chick? or A 2 bodied chick? or 2 premature or mini chicks? or just a super mutant freak-out creatue chick? what if ?