My idiom

1.  When pigs fly.

2.  About something that will never happen, like someone saying something that is impossible.

3. "I'm gonna do a double back-flip on the ground.""Just like pigs can fly!"

4. Dad always says, "Oh fire in the whole." and he only says it when he farts.

5. When pigs fly, it has been a traditional Scottish proverb, was first written in 1586 in an edition. It's also a way to joke that someone will never do something or something will never happen. Example: "Do you think you will ever work at that company again?" Reply: "When pigs fly!"