In Harry Potter and the Goblet of Fire, David Tennant’s improv changed the film’s Mad-Eye Moody twist. The fourth Harry Potter film introduced several major new characters to the franchise. As Hogwarts students competed in a magical tournament alongside students from the Durmstrang Institute and Beauxbatons Academy of Magic. Voldemort (Ralph Fiennes) made his first proper appearance. As did Cedric Diggory (Robert Pattinson). Barty Crouch Jr (David Tennant) and Alastor Mad-Eye Moody were two of the new characters who played pivotal roles in the Goblet of Fire story (Brendan Gleeson).

Moody was an important character in the film, as he aided Harry Potter during the Triwizard Tournament. However, neither Harry nor anyone else at Hogwarts was aware that Mad-Eye Moody was a fake. The twist in Harry Potter and the Goblet of Fire was that the seemingly cruel. But helpful teacher was Barty Crouch Jr. in disguise. Using Polyjuice Potion, a Voldemort follower subdued Moody and ensured that Harry Potter would be chosen from the Goblet of Fire. While this twist occurred in J.K. Rowling’s book as well, the film adaptation included a significant change that could have alerted unsuspecting viewers to what was going on.

When David Tennant was cast in the role of Barty Crouch Jr. He was given the creative license to make the wizard his own. Tennant worked on a few unique tics for his Harry Potter character. Crouch’s most distinctive habit is licking his lips like a snake. Neither the source material nor the script for Harry Potter and the Goblet of Fire called for Tennant to have this trait. But director Mike Newell liked the improvisation. Brendan Gleeson, who had to play Mad-Eye Moody as Barty Crouch Jr., adopted this change and added a few of his lip licks.

While the Crouch Jr./Mad-Eye twist was always going to be present in Harry Potter and the Goblet of Fire. Tennant’s improvised lip-licking habit added a new dimension to the reveal. Following the second task of the Triwizard Tournament. Mad-Eye Moody displayed Crouch’s licking tic for the first time. It happened even while Moody was speaking with Crouch Sr. Who recognized his son’s tic right away. Crouch Sr., on the other hand, was unable to tell others about this information because he died shortly after meeting his son in disguise.

Those who have read J.K. Rowling’s Harry Potter books may have guessed the Mad-Eye Moody twist was on the way. But David Tennant’s improv gave the film away to tease it out to keen viewers. Tennant licked his lips a lot in his scenes as Barty Crouch Jr. Those who picked up on this habit and then saw Moody do the same thing might have predicted the big twist in Harry Potter and the Goblet of Fire.