When pigs fly

Meaning: Something that will never happen

Significado: Algo que nunca sucederá

Traducción literal: Cuando los cerdos vuelen

Real examples:

Example 1: “«Maybe you’ll understand when pigs fly,» he said, offending Miss Thornburgh, who thought he was questioning her intelligence.” (From the book No Sleep Till Deadtown)

Example 2:

Example 3: