Any embryo that could start developing in such a tiny egg would likely stop and die somewhere along the way due to lack of space, missing yolk (often there's no yolk or a tiny one), etc.
Or they hatch with problems. Not a good idea to me.Always seems to be some curiosity about trying to hatch tiny chicks from small eggs, twins from double yolkers, etc. Mother Nature obviously disagrees, which is why any oddball eggs are generally not viable for hatching.
Fairy, fart, wind, rooster eggs are usually from a tiny piece of tissue breaking loose from the reproductive tract, or an immature ova(yolk) and the body forms an egg around it. Color can be darker than 'normal' as the pigment coating released has to cover a much smaller area so is thicker. Can happen with any age layer, but more common with older layers.Has anyone ever opened one?
Was there a tiny yolk?
once did that by mistake thought my bantam laid it but I don't think she did so ended putting it under a broody and after a week of the chicks hatching decided to crack it open and saw it started to develop but died most likely due to lack of space or yolk but now I try to keep bantams separate so I know what egg hatch