Regardless of your age or whether you've read any of the Harry Potter books, there's a pretty good chance you've at least seen one (or all) of the eight Harry Potter movies.

For those of you who did read the series growing up, you're about to feel a bit older—and that's because today marks the 20th anniversary of the publication of Harry Potter and the Philosopher's Stone, or, as it's known in the U.S., Harry Potter and the Sorcerer's Stone. That's right: On June 26, 1997, the first of what would become seven books, eight films, and a $25 billion franchise hit bookshelves for the very first time.

The launch of the Sorcerer's Stone also paved the way for quite a few young actors who became international superstars who grew up before our very eyes over the 10 years when the films were shot and released.

But while the last film of the original Harry Potter series wrapped in 2011, that doesn't mean its stars quit growing up. In fact, quite a few of the male cast members underwent serious body transformations—and some got so jacked (yes, jacked) that you might not even recognize them at first glance.

Check out the best Harry Potter male castmember body transformations—and prepare to be stupefied.