He is a sexist 'pig'. = He is a 'male chauvinist pig'. [=he is a man who thinks women are not equal to men]
The train station will be renovated 'when pigs fly'. [=it will never be renovated]
“This time I think he'll ask me to marry him!” “Yeah, and 'pigs might fly'.”
(..) direct from the local smokehouse. You're all experienced butchers yourself. I assume you are aware that the humble pig can be cooked from nose to tail, everything but the squeal. I can offer you nine cuts at the best prices in all of Christendom. (..)2017 Baby Driver