So there is a lot of set up to this story:

A few weeks ago Parker asked what was 'in' cheese. I told him that cheese and yogurt are made from milk.
Then a week or two later we pass a big truck on the freeway carrying a GIANT load of hay. I explained to Parker that farmer's grew the hay and that they were bringing it to be given to horses or cows, and then the cows can make milk.
Then another week later we're in the store and he helps me grab the last yogurt off the shelf and put it in our cart. He asked why there were no more. So I told him about how the store gets shipments and then they would restock the yogurt.

He stops and thinks for a minute and says "Yogurt comes from hay." I say "Oh, really?" and then he explains the whole process:
farmers plant hay
get the hay on a truck
bring it to the cows
cows eat it and make milk
make yogurt
put lots of yogurt on a big truck to bring to Walmart
put it on the shelves
put it in the cart
buy it, bring it home and put it in the fridge
eat the yogurt.

I was amazed! I couldn't believe he pieced together those separate conversations. This kid is too smart for his own good. And totally too smart for MY own good.