Game of Thrones' most shocking moment is undoubtedly season 3’s Red Wedding, which was made even more gruesome than the books due to a significant change made to the character of Robb Stark’s wife. In Game of Thrones’ episode “The Rains of Castamere,” Robb and Catelyn Stark attend the wedding of Edmure Tully to Walder Frey’s daughter, which only occurred because Robb broke his marriage pact with the Freys in order to marry Talisa Maegyr (Oona Chaplin). At the event, later labeled the "Red Wedding," Robb, Catelyn, numerous Stark allies, and Talisa were brutally murdered at the hands of the Freys and Roose Bolton.
While HBO’s Game of Thrones took multiple liberties in adapting George R.R. Martin’s books, one of the most controversial changes occurred in season 2 with King Robb Stark’s soon-to-be wife Talisa Maegyr. In the books, Robb had married young Jeyne Westerling, the daughter of an impoverished nobleman whose house served the Lannisters. After sleeping with her during an expedition to the Westerlands, he primarily married Jeyne to preserve her honor. In the show, however, Jeyne was changed to a new character named Talisa, a healer and noblewoman from Volantis. Robb's marriage to Talisa gave him a new motive by having Robb break his oath to the Freys due to love instead of duty, with Talisa becoming pregnant with his child before Game of Thrones’ shocking Red Wedding.
The Red Wedding in Game of Thrones is very similar to that of the books, though the massacre was made far more brutal due to this change from Jeyne to Talisa. In the books, Jeyne never went to the Red Wedding with Robb because they didn’t want to offend the Freys, plus she was also never pregnant due to her mother giving her potions to prevent conception. Talisa’s circumstances in the Red Wedding were far different, which contributed to one of the most horrifying deaths in Game of Thrones history. Talisa attended the Red Wedding alongside Robb, with the Volantene noblewoman also being visibly pregnant with his child. Before Robb is shot with an arrow and Game of Thrones' House Frey begins to slaughter the Stark allies, viewers witness one of the Frey men brutally murdering Talisa (and her unborn child), stabbing her to death in her stomach, a pointed focus on her womb.
While it’s unclear if Game of Thrones’ primary motive in making Talisa pregnant was to contribute to such a shocking on-screen moment, her death officially marked the ruthlessness of the show’s violence. The visceral scene of a pregnant woman being stabbed in her stomach was one of Game of Thrones’ most repulsive moments, with such cruelty being surprising for television, even a show as outrage-prone as Game of Thrones. What’s more emotional about Game of Thrones’ change is that viewers actually became attached to Talisa Maegyr, which can’t necessarily be said of Jeyne Westerling. In the books, Robb’s entire story is told from the perspective of other people, with only being discussed in passing or in conversations with Catelyn Stark before her death. The death of Jeyne wouldn’t have been as shocking as Talisa’s in Game of Thrones had they not changed both her and Robb’s characters, but the series took an extra step in its gore by making the show's version of his wife pregnant.
According to Robb Stark actor Richard Madden (via Rolling Stone), Talisa’s death was necessary in order to finalize his story and army. Had Talisa lived while pregnant, viewers would have been left with theories about Robb’s son returning to avenge his father’s death, similar to Robb’s Game of Thrones storyline being based on avenging Ned’s brutal murder. Game of Thrones’ change to Talisa and Robb made their story far more tragic, as their life and plans were cut short by the cruelty of the war in the series. Unlike the dilemma Tyrion has about killing Cersei Lannister in season 8 due to her unborn child, Game of Thrones’ Red Wedding proved that nobody was safe in the show - not even an apolitical woman carrying a child.