The Harry Potter movies made some interesting changes to how the Wizarding World’s magic functioned compared to the source material, and one of the most confusing alterations made during the adaptation process was made even worse in a later installment. Many fans were introduced to the franchise via the Harry Potter movies. So, they wouldn’t have been aware of any book changes upon their first watch. The jump from the pages of JK Rowling’s work to the big screen meant some alterations were necessary to accommodate the change in medium, but those tweaks weren’t always honored in the sequels.

The cast of the Harry Potter movies was tasked with bringing together the changes made to the books, although the endeavor wasn’t entirely the responsibility of the actors. There’s no denying the depth of Harry Potter lore, nor the fact that certain facets work better in the books than they do in the movies. As such, some of the tweaks made stick out a little more than others. One change in particular made for the second installment in the series was particularly noticeable, and it raised a very specific question further down the line.

The Chamber Of Secrets’ Polyjuice Potion Book Change Explained

The second Harry Potter movie didn’t change Harry & Ron’s voices when they transformed

Almost every Harry Potter fan will know the function of Polyjuice Potion. It allows whoever drinks it to transform into the person of their choosing – if their DNA is added into the mix in advance. The potion isn’t used particularly heavily throughout the franchise, but it does have some prominent moments. One of the most iconic is Harry Potter and Ron Weasley taking the form of Vincent Crabbe and Gregory Goyle, so they can quietly interrogate Draco Malfoy. The movie moment is almost a beat-for-beat interpretation of the book scene, except their voices don’t change in the adaptation.

In the book, Harry and Ron don’t just take on the Slytherins’ physical appearance, but they also speak with Crabbe and Goyle’s voices.

In the book, Harry and Ron don’t just take on the Slytherins’ physical appearance, but they also speak with Crabbe and Goyle’s voices. However, in 2002’s Harry Potter and the Chamber of Secrets, Daniel Radcliffe and Rupert Grint still provide the voice performances for their characters’ magical disguises. Crabbe and Goyle actors James Waylett and Josh Herdman are thrust into starring roles for the sequence, but Radcliffe and Grint don’t completely hand over the reins to their concealed characters. It may seem like a small change, but it’s highlighted two movies later.

Barty Crouch Jr’s Polyjuice Potion Changed His Voice In The Goblet Of Fire Movie

The fourth Harry Potter movie retconned The Chamber of Secret’s book change

A huge twist in both versions of Harry Potter and the Goblet of Fire is the reveal that Alastor “Mad-Eye” Moody has been Barty Crouch Jr the entire time. The method of hiding himself is the same as Harry and Ron used in The Chamber of Secrets – Polyjuice Potion. Interestingly, the movie version of Mad-Eye Moody has the speaking voice of actor Brendan Gleeson. If The Goblet of Fire were to abide by the rule established in The Chamber of Secrets, then technically, Moody should actually be voiced by David Tennant – who plays Barty Crouch Jr in the 2005 adaptation.

This feels like a big miss from the creative team working on the movies. What makes it even worse is the fact that the screenplays for both movies were written by Steven Kloves. That being said, it depends on whether Kloves added notes to his scripts about how Polyjuice should affect the user’s voice – if at all. The Chamber of Secrets and The Goblet of Fire were directed by Chris Columbus and Mike Newell, respectively. So, there could have been a change in course due to this behind-the-scenes move.

There Could Be An In-Universe Explanation For Why Barty Crouch Jr’s Voice Changed

David Tennant’s Harry Potter character could have made a superior batch of Polyjuice Potion

Although the Polyjuice Potion voice disparity across the Harry Potter movies hasn’t been directly addressed, there could be a canonical reason why Harry and Ron’s voices didn’t change in the second movie, but Barty Crouch Jr’s did in the fourth. One rather grounded (but salient) theory all comes down to the skill of whoever brewed the potion in question. The potion consumed by Harry and Ron in The Chamber of Secrets was the result of Hermione Granger’s hard work. For all the brilliance and intelligence of Emma Watson’s character, she’s still only a second year in the franchise’s first sequel.

While it was impressive Hermione was able to make a Polyjuice Potion at all, it could have been an imperfect attempt.

So, while it was impressive Hermione was able to make a Polyjuice Potion at all, it could have been an imperfect attempt. This would explain why the transformation of Harry and Ron happened on a physical level, but the effects didn’t extend to their voices. Inversely, Barty Crouch Jr is one of the many powerful dark Wizards in Harry Potter lore. He may be a villain, but he’s older and more experienced than Hermione. As such, the effects of his Polyjuice Potion skills are more likely to accurately reflect the description in the Harry Potter books.

Harry & Ron Keeping Their Voices As Crabbe & Goyle Is Probably A Production Quirk Too

Keeping Radcliffe & Grint as the voice of their transformed characters helped keep track of who was who

The stark truth of the matter is that certain concessions sometimes need to be made when adapting a book. In The Chamber of Secrets, the movie does a good job of helping the audience remember who Harry and Ron have each transformed into – even before voices are considered. Crabbe and Goyle are always together, so it’s already difficult to recall who is who. The film fixes this by having Harry (disguised as Goyle) forget to remove his glasses until Malfoy points them out. This doesn’t happen in the book, as Harry removes them immediately, with Goyle’s eyes not needing correction.

Harry openly points out in the Chamber of Secrets movie, ” We still sound like ourselves ,” which negates the possibility of it being a matter of audience perception.

If Harry and Ron’s voices had changed, Harry’s glasses staying on Goyle’s face may have been enough to tell them apart. Unfortunately, the story doesn’t allow this as a long-term solution. As a result, the only remaining option to stop the movie from becoming hard to follow is to have Radcliffe and Grint continue to voice the characters. The solution isn’t perfect, as Malfoy should surely realize his friends sound very different – and exactly like Harry and Ron. On the other hand, the second Harry Potter movie is left with little else it can do to keep things clear.

Regarding Moody’s voice in The Goblet of Fire, the movie would have suffered if it had decided to remain consistent with the change The Chamber of Secrets had already introduced. If Brendan Gleeson had spoken with David Tennant’s voice throughout, it would have been fairly obvious that something was amiss. This would have resulted in the brilliant twist of Barty Crouch Jr’s reveal becoming far less effective than it was. So, although it creates an issue with the movies’ lore, the Harry Potter creative team made the right call.