Answer: when you have a city person forgetting that chickens aren't a machine.
I'm serious. There has been a hilarious episode in Malaysia at the moment, where a complaint to the Consumers' Asscociation of Penang (CAP) led to a kerfuffle where eggs were being tested to see if they were...wait for it..."fake" eggs from China. They looked like eggs - with a shell, yolk and white, but were not, according to a spokesman from CAP, real. Someone, they said, was faking eggs in (according to me) what must surely have been an incredibly complicated and expensive process costing ten times the price of a real egg.
CAP said they were weird shapes and odd colours...and had no taste. Excuse me while I roll around the floor laughing.
I was brought up on a poultry farm. Hens are not machines. They are living, breathing creatures. They lay brown eggs, white eggs, odd shaped eggs, huge double-yoked eggs, eggs with blood spots, pale yolked eggs, dark yolked eggs (according to what they have been eating), eggs with ridges on the shells, and so on. Such eggs are usually sold to places like biscuit factories, cheaply.