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'.”
(..) Not a single one. Stupid, stuck-up town. "Stupid, stuck-up town." Yeah, check it out. I'm sorry, are those two pigs? Wait till you check out the back. "Porking." It's funny, right? Yeah, makin' bacon. That is funny. (..)2016 TvShow: Bones Title: The Movie in the Making Season: 11 Episode 18