Some get boob jobs (like, REALLY huge boob jobs).
Other suffer from some serious makeup disasters.
Still others lose a lot of weight, while a few hit the gym and many simply grow up. Way, way, way, way up.
Indeed, there are any number of reasons why celebrities alter their looks, but that doesn't make it any less dramatic to feast your eyes on some of the more extreme transformations in recent memory.
Remember when Uma Thurman looked like, well, Uma Thurman?
Remember when Nick Jonas was a lovable very young singer with a mop top, as opposed to a six pack?
Remember when Drew Carey, Jonah Hill and Jennifer Hudson all weighed nearly twice as much as they do now?
No? Go back in time and remind yourself then. We've collected 17 of the amazing celebrity transformations in the above photo gallery and we encourage you to click away.
Because these must been seen to be believed.