Where do they get this from??!!

So on our way home from filing our taxes, I asked our children if they remember when the Arby's and the Walmart and the other various shops were built. Some replies I received was kinda(H),maybe(Z), and no(J).  However, the one to remember came from,......,,, Noah! His fabulous reply was, "No Mom, you know why? It was before I was born. I was just a rotten egg in your stomach then." All serious and not once laughing, unlike his sister, brothers and dad! (I didn't laugh though, was too flabbergasted to!) We have to ask where does he come up with this??!! We figured out where this one came from anyway. The game many play of last one there or you're a rotten egg. Noah says he's always the last one there so he must be a rotten egg. Hmmm. Should I be proud of his medical knowledge of where he came from or saddened to think he thought he was a rotten egg or amazed that 5 yr olds can pull things out of their mini computer brains like this? I felt a little of all three and maybe its just a mom thing, but I felt mostly sad because he believed it! Our precious Noah. You are certainly not a rotten egg but instead a wonderful blessing and bundle of pure joy for your family. We all love you SO much, little soon to be 6 yr old fellow!