Yup, lived on a egg-layer farm for five year w/ 9000 hens.
"Jumbo" or "double-yoked" eggs aren't that rare.
Lots of fun deformed & strange looking eggs i got to see.
Egg inside an egg isn't as common though.
We also had hens growing up also. I remember one time I was 12 and making a cake, it called for three eggs:
Cracked the first one, normal.
Cracked the 2nd one... Two yokes.
I sat there for a moment, wondering what the HELL we were feeding those things when something occurred to me...
"S***... do I put in the THIRD egg, or do I stop?!"