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'.”
(..) because it thought that her hair was a nest. Okay, fine. I will call Lonnie. He will talk to me before he talks to... - What, a pig? - A cop! Just find my son, Hop. Find him! Dr. Brenner. This way, gentlemen. (..)2016 TvShow: Stranger Things Title: Chapter One: The Vanishing of Will Byers Season: 1 Episode 1