The Polyjuice Potion Detail In Harry Potter That Makes No Sense To Fans

Though there are dozens of potions mentioned and used throughout the "Harry Potter" film franchise, one of the most iconic wizarding concoctions in the entire series has to be Polyjuice Potion. The potion first appears in "Harry Potter and the Chamber of Secrets," when Harry (Daniel Radcliffe) and Ron Weasley (Rupert Grint) use it to impersonate Crabbe (Jamie Waylett) and Goyle (Josh Herdman). The potion allows whoever drinks it to take on the appearance of another person — and requires using a piece of that person's body as an ingredient, most often a strand of their hair.

Polyjuice Potion also plays a major role in "Harry Potter and the Goblet of Fire," wherein the dark wizard Barty Crouch Jr. (David Tennant) uses the potion to pose as Hogwarts teacher Mad-Eye Moody (Brendan Gleeson) for the entire school year, all while secretly scheming to hoodwink the officials of the Triwizard Tournament. The potion appears again in "Harry Potter and the Deathly Hallows – Part 1," when it's used to change members of the magical resistance group, the Order of the Phoenix, into copies of Harry to serve as decoys for the dark wizards hunting him. And yet, as many fans have pointed out over the years, the potion itself seems to function very differently across all of these movies — almost to the point where it seems like the filmmakers must have made a mistake.

When the Polyjuice Potion is used in "Chamber of Secrets" and "Deathly Hallows," it's easy to tell which characters are which because they all keep their original voices despite changing their physical appearances. However, between those two movies in "Goblet of Fire," Barty Crouch Jr.'s voice appears to change into Mad-Eye Moody's voice. The lack of consistency makes no sense to fans, as shown by this recent Reddit post asking why Barty's voice changes in the film when Harry and Ron's voices didn't change with their appearances in "Chamber of Secrets."

"To not spoil the plot for the fourth movie," explained u/Radixmesos. "In the books the [v]oices change." Indeed, in the "Harry Potter" book series, the character's voices change every time they take Polyjuice Potion, not just when it's convenient for the plot's sake. U/PetevonPete echoed this claim, saying "Because the filmmakers thought the audience would be too stupid to keep track of which was Ron and which was Harry, but in GoF it couldn't be avoided."

Some users were more critical of the decision, saying that the inconsistency between the films showed a lack of experience from the filmmakers. "They made poor directors choices in the second movie and weren't consistent," wrote u/karp1234. "This was just a stupid decision made by the director," echoed u/Birdtheword3o3. 

But commenters on a similar Reddit thread offered another potential explanation — one that speculated the incongruity was simply the result of a detail that was too subtle for most viewers and never properly clarified. "It could be that Barty Crouch Jr[.] is just an amazing voice impersonator," theorized u/Clearin. "I'm pretty sure that's what they were going for," agreed u/martythedrunkunicorn, citing the character's accurate impression of Hagrid (Robbie Coltrane) in the scene right before the Polyjuice Potion wears off and Barty's true identity is revealed.

Whatever the real reason, it's clear that this maddening inconsistency across the "Harry Potter" films is a major problem for fans of the series, and one that, in hindsight, also seems avoidable.