Mushed bananas, cooked carrot mush, cooked potato mush, mushed strawberries maybe... And he MIGHT have these symptoms if he has a blockage:
Unable to stand or refusing
Not wanting to eat or drink
Un-activeness
Off colored comb or wattle
Show this to your dad.
He will die if it gets caught in his digestion track and stays. If it gets caught he needs surgery. Monitor him for at least 3 days. If he shows signs of illness please take him to the vet if you care about him.
Eating a sock could indeed kill him. Do not give him socks.. Take him to a vet.. He might need surgery if the sock pieces get stuck. And why are you trying to stop his crowing..? It's a natural rooster habit and in my opinion it sounds nice.