video showing a man cracking a giant egg to reveal another fully formed egg inside .
the instance is extremely rare , it 's caused when the hen is in the process of forming an egg -rrb- , were laid by one of his hens , exclaiming : ` the big egg has another normal egg in it ! ' while the instance is extremely rare , it 's thought that a shock , or stress causes a contraction , forcing first egg to reverse its course .