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'.”
(..) our illustrious King Julien XIII, self-proclaimed lord of the lemurs, et cetera. Hooray, everybody. He's got style. What is he, like, king of the guinea pigs? I think it's a squirrel. Welcome, giant pansies. Please feel free to bask in my glow. -Definitely a squirrel. -Yep. Squirrel. (..)2005 Madagascar