When I got my first two hens (well, the first THIS time...) the lady told me that one of them will occasionally lay a double-yolk egg, so I wouldn't be surprised or worried when one showed up... she didn't know WHICH hen, as of course they lay the eggs inside the coop in the nesting boxes... so I don't know which hen either.
Weeks went by and we got eggs, usually one a day, sometimes 2, sometimes they would skip a day... both laying brown, but one several shades lighter than the other.
Hilary didn't say anything but the first time I gathered eggs upon our return from Michigan and went to put them in the egg carton, I saw THIS:

Of course I was without camera then so I saved that monster egg until I got a new camera! It is clear to me that the double-yolk egg-layer is definitely the one laying the lighter brown eggs... however I STILL don't know WHICH hen it is...
A closeup to compare...

So last Friday I had myself a one-egg breakfast... after I cracked the egg into the bowl to take this picture, I thought "Duh! Should have taken a video to PROVE that both yolks came from the same egg!" Great thought BUT I was the only one up and you can't run a video and crack an egg at the same time with only two hands {sigh}.

I just kept thinking to myself, this explains to me why people get *that look* on their faces when I share that my second daughter weighed in at TEN POUNDS FIVE OUNCES at birth... yeah, that hurt! And I think my hen must have felt the same way!!!
Uploading the above pictures I realized I never blogged the other end of the spectrum... before the pint-sized chicken died of heat stroke, she was quite productive - hers are on the right, smaller and lighter...

Again a close-up to compare

One thing I can say is no matter the size, fresh all-natural eggs sure are good!!!