We've been jamming out to Iggy Azalea and Britney Spears' "Pretty Girls" ever since it was released, and you can have Little Mix to thank for that catchy track! The girl group revealed that they wrote the song for their third album, but eventually decided not to include it.

"We've been away a while because we wrote an album, sat with the record label and we thought, 'Nope, it's not good enough,'" Jesy Nelson told The Sun. "We recorded a whole album but we're perfectionists and knew we could do better. So we scrapped it and started again."

Then, the song got picked up by Iggy and Britney!

Of course, they're not the only artists to write songs for other singers. Click through to see songs you didn't know were written by other artists, and let us know which one surprised you the most in the comments!