Yes, I clicked in to see if this was an IVF thread.
I can by cartons of double-yolked eggs from a vendor at one of the local farm markets. Only rarely are his jumbo eggs not double yolks. They are entertaining to show kids but have too much yolk volume for using in recipes.
I think the important question is when did eggs start coming in cartons of 10? I’ve only ever seen them in cartons of 6 or 12.
Where was it that I saw an egg inside another egg? Was it on TV or in real life? I can’t remember.
Years back I bought a dozen eggs from the supermarket, and every one of them was a double-yolker. I imagine that they were rejected during the quality control phase or something (perhaps weighing too much for the standard sized egg), and ended up in their own special carton.
When I moved to Germany 
Well, if we were Facebooked with each other I’d suggest you probably saw it on my thread there.
Yep, those are the videos I saw! I didn’t think I was going mad…