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'.”
(..) Where are you? Mac, where are you? Jesus. I got you, motherfucker. I killed you, you fuck. Jesus. You killed a pig. Do you think you could have found something bigger? Fuck you, Poncho. Fuck you. - Where's the girl? - Shit. (..)1987 Predator