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'.”
(..) You alright? Haven't been North before? Never seen snow before. Beautiful, eh? I can breathe again. Down south the air smells like pig shit. - You've never been down south. - I've been to Winterfell. That's the North. How do you live up here? How d'you keep your balls (..)2017 TvShow: Game of Thrones Title: Beyond the Wall Season: 7 Episode 6