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'.”
(..) terrestrial and satellite, 'and... No! 'On all British networks, terrestrial and satellite, 'and have full unsimulated sexual intercourse with a pig. 'I don't understand!' The video ends with a series of technical specifications for the broadcast. Why are you doing this? "Mike!" It's real. She said pig. Sex with a pig. They want me to have sex with a pig? Live on television this afternoon. But what...? Who...? (..)2011 TvShow: Black Mirror Title: The National Anthem Season: 1 Episode 1