Harry Potter's David Thewlis Explains Why His Original Werewolf Transformation Was Too Scary For Kids

Looking back at the live-action adaptation of the Boy Who Lived, one entry in the franchise marked a turning point for the "Harry Potter" movies. "Harry Potter and the Prisoner of Azkaban" drew a line through the Hogwarts courtyard as a more serious and sinister chapter, courtesy of the now-Oscar-winning director Alfonso Cuarón. Besides being another mystery during term time, "Prisoner of Azkaban" brings terror in the form of soul-sucking Dementors, a murderous escapee, and a new teacher with a monstrous secret.

No stranger to being a threatening force in the likes of "Wonder Woman" and "The Sandman," David Thewlis played the caring but cursed mentor to Harry (Daniel Radcliffe), Professor Remus Lupin, debuting in the franchise's third installment. An unnerving enough tale as it is, things get even more dangerous in the film's final act when Lupin's monstrous side reveals itself in all its gangly, grotesque form, giving us a kind of werewolf we hadn't seen before. A CGI beastie that still holds up since its debut in 2004, it turns out that Lupin's transformation isn't what was initially planned. The real shift from man to beast was a lengthy process that Warner Bros. eventually backed off from.

In a franchise that is filled with antagonists and otherworldly creatures brought to life through prosthetics and incredible make-up, unfortunately, Professor Lupin's wolfish other side isn't one of them. David Thewlis revealed on "This Morning" that even though a pixelated version of Lupin's beastly form was used in the final cut, there was a much more monstrous first attempt. "It was prosthetics when we shot it, but we shot it in such a way that was considered a little too scary for the kids, and I think it was done in CGI in the end," he explained.

Going into more detail about what kind of shape-shifting was considered that we didn't get to see, the former Defense Against the Dark Arts teacher added, "Originally, I used to have blood in my cheeks that poured out of my cheeks, and I threw up." Lovely stuff. While it might have been wiser not to mentally scar youngsters in theaters thanks to the change they didn't get to see, the transformation we ended up getting still came with a downside when working on set.

While we didn't see the "Harry Potter" star get too hairy in "Prisoner of Azkaban," the film still boasts a pretty unsettling sight of Lupin growing in height and howling at the moon. But while becoming a werewolf might be worth checking off the list of an impressive career, Thewlis couldn't deny that it had its downsides (via YouTube). In an interview following the film's release, Thewlis explained it was a very uncomfortable part of the role. When it came to becoming less Lupin and more lupine (how many of you just got that now? Admit it), Thewlis recalled one occasion that saw him go slightly more method actor than necessary.

"You have these lenses in. You can hardly see anything, and a light would be blinding to you. And we were on a very dark set, and I was led out, and it was the middle of summer, and they opened the big studio door, and the sunlight hit my eyes, actually, and I had the teeth still in, and I actually was like, 'Ahhh!'" Seeing an esteemed actor like Thewlis curse the heavens baring teeth, claws, and contact lenses like fish bowls must have drawn a somewhat understandable reaction from passersby. Thank Dumbledore for CGI magic, right?