When pigs fly

"When pigs fly" is a silly expression that people use when they want to say that something is very unlikely to happen. It's like when your parent says "sure, you can have a giant ice cream sundae for dinner... when pigs fly!" They don't really mean that pigs are going to fly, they're just saying that it's not going to happen. Pigs can't actually fly because they don't have wings and they're too heavy. So next time you hear someone say "when pigs fly," just remember that it's just a funny way of saying that something is not going to happen.