My dark Cornish hatched a brood of four chicks today. This is her second brood this year. I was surprised they hatched because about 10 days ago DH collected eggs and accidentally collected the hatching eggs as the hen had been off them temporarily. It wasn't till several hours later that I realized what had happened. The hen readily accepted them back when I took them out to her but I was concerned they had been in the house too long.
One did work himself into the "shrink wrapped" stage. He had chipped away the shell but was stuck in the membrane. After about 24 hrs of this he was still chirping so I cut a tiny hole in the membrane. A few hours later he was out.