Harry Potter and the Goblet of Fire finally put away the kid gloves in. the franchise and revealed the danger and coming storm tied to Lord Voldemort, but Voldemort wouldn't just appear out of nowhere, as he had already spent years using his followers to find ways to amass enough strength to finally emerge at full power. Eventually, this plane came to fruition during the Triwizard Tournament when Harry Potter was mysteriously chosen as the fourth contestant. While many viewers and readers remember that Harry was chosen, those that don't remember every detail may have forgotten who the culprit was that put Harry's name in the Goblet of Fire.
Part of what helped establish Harry Potter and the Goblet of Fire as the first mature book of the series was the mystery of who put Harry's name in the Goblet and the murder and deception tied to it. Since Voldemort's followers could be anywhere, it amped up the paranoia and showed how the Triwizard Tournament may have been the last moment of peace for the Wizarding World for a few years, but even though Harry's name being put in the Goblet could be a mystery, the culprit would soon be revealed as Death Eater, Barty Crouch Jr.
Barty Crouch Jr. was a devout follower of Voldemort and was the first to escape Azkaban prison in over 300 years. It's said that he also played a role in torturing Neville Longbottom's parents. While he played a small role in the Voldemort's grand scheme, his methods were as unforgivable as they were deadly and precise. Part of his plan to fake his death included having his mother serve as his decoy in Azkaban so that Barty would no longer exist when she died. At which point, he was trapped in his father's Imperious Curse, which kept him from completing his plan. Nevertheless, Voldemort helped Barty break free, and he then kidnaped Alastor Moody and took his place with a Polyjuice Potion.
As the new Defense Against the Dark Arts professor, Barty used his Moody disguise to walk freely in Hogwarts and get close to Harry Potter and his friends. He also aided him in small ways through the Triwizard Tournament, but no matter how helpful he appeared, his actions were always to get Harry closer to Voldemort. That said, the Confundus Charm he placed on the Goblet of Fire put his plan in motion.
Because the charm Barty placed on the Goblet of Fire was so powerful, he could make it believe Harry was from a different school. Therefore, when it came time to choose contestants, Harry's name appeared to everyone's surprise. Ironically, while the charm itself would pale in comparison to a killing curse, it was Barty's charm that inadvertently led to countless deaths at the hands of Voldemort. However, following the return of Voldemort, Barty was soon discovered by Dumbeldore, and the real Moody was found. In the end, he was killed by a Dementor's Kiss.
In the grand scheme, Barty Crouch Jr. was but a blip in the larger battle between good and evil in the Wizarding World. However, what he had done in the short time he was given fundamentally altered the course of history for dozens of witches and wizards. But being that he was the one who put Harry's name in the Goblet of Fire, it's hard not to ponder how different things would have been had he been discovered early or never put Harry's name in the Goblet at all.
