Part of what makes the Harry Potter series so enjoyable is all the supporting characters in it, both good and evil. The villains in Harry Potter are incredibly memorable, whereas the characters who stand for good are extremely likable. Moreover, some characters are more than they seem. One of the biggest twists in the Harry Potter series is that Severus Snape acted as a double-agent throughout in service to Albus Dumbledore. This caused Snape to kill Dumbledore to prove his loyalty to Voldemort. Despite Snape's contempt for Harry, he was still inspired to fight against Voldemort because of his love for his mother.

While Snape is the most notorious double agent in Harry Potter, he was not the only one. Other characters like Professor Quirrell, Peter Pettigrew, Mundungus Fletcher, and others played both sides during the Wizarding War. Moreover, a lengthy theory from Zach Hansen, initially posted on Reddit, suggests another major character was secretly a servant to Voldemort the entire time, and not only is the answer heartbreaking, there's an abundance of evidence to support it.

Rubeus Hagrid played a significant part throughout Harry's journey, but his biggest role occurred in the young wizard's first year. Hagrid is the first character from the Wizarding World Harry encountered, and is the one who ultimately rescued him from the Dursleys to set him on the path to Hogwarts. Hagrid is the half-giant gatekeeper and groundskeeper at Hogwarts who was notoriously expelled from Hogwarts after he was framed by Tom Riddle, who convinced the Hogwarts headmaster at the time that Aragog was behind the attacks when it was really the Basilisk.

Despite Hagrid's dark past, the Harry Potter series portrayed him as a gentle giant who is a major figure for Harry. However, Hagrid committed some suspicious acts in the series as well that could make someone believe he was secretly working for Voldemort the entire time. The Harry Potter series is full of hidden details laid out early on that eventually play into the overall mystery of the story. For Hagrid, there is a lot more evidence that supports the idea of him being a Death Eater than many would like to admit, right from the very beginning of the series.

Several pieces of evidence support the theory that Hagrid was on the side of evil the entire time, and one of the biggest occurred in Harry Potter and the Sorcerer's Stone. At various points, Hagrid displayed a level of magic that he wouldn't be capable of doing since he was expelled in his third year at Hogwarts. Yet, Hagrid infamously gave Dudley a pigtail after he arrived on the island where the Dursleys and Harry were hiding out. While the simple act of giving someone a pigtail might not seem like much, transfiguration is challenging and only taught at the N.E.W.T. level, making it strange that an expelled student like Hagrid was able to perform such magic.

When Harry and Hagrid left the island, the half-giant also said he flew, and that also raises some alarm bells since Hagrid can't fly on a broom, there were no creatures around, and he doesn't have Sirius Black's motorbike. If Hagrid truly flew to the island, then there's a chance he learned the ability from Voldemort, one of the only characters in the series who does it. Unaided flight is rare, and because Voldemort has passed it down to close allies like Snape, Hagrid is another who might've learned how to do it from the Dark Lord. While the Harry Potter series revealed early on that Hagrid does possess impressive abilities despite not having a wand or being able to legally use magic, he strangely doesn't fight against the Death Eaters until the very end, when Voldemort's defeat is clear. Hagrid's magical abilities don't add up based on his Hogwarts past, and it certainly raises suspicions.

• In Order of the Phoenix, Dumbledore tasks Hagrid with a mission that would seemingly be out of his depth.

To be an effective double agent, one must have a different and convincing persona to gain the trust of whoever they are trying to deceive. Hagrid might be a character who came across as someone with a lot of empathy, but he also had some notable faults. Hagrid was typically clumsy throughout the series and didn't tend to do a good job of keeping secrets. For instance, Hagrid revealed a lot about the Sorcerer's Stone to Harry, Ron Weasley, and Hermione Granger, and also let out information regarding Sirius Black. However, later on in the series, Hagrid is sent out on a mission by Dumbledore to convince the giants to join in the fight against Voldemort. At first glance, Dumbledore giving Hagrid the mission made sense given his background. However, . The Death Eaters ultimately convince the giants to join their side, but it's unclear how they knew of their whereabouts, and there's a chance Hagrid provided them with the location.

Because Hagrid's mission in Harry Potter and the Order of the Phoenix is a bit of a leap, his persona as a bumbling giant could've been misdirection all along. We've seen Professor Quirrell adopt the same type of personality, so having Hagrid do something similar isn't too much of a stretch. By creating this fake personality, Dumbledore and others would never suspect Hagrid of being capable of doing much to threaten, but it would slip out from time to time. In many ways, it's the opposite of what Snape does to gain Voldemort's trust while truly serving Dumbledore.

Hagrid secretly serving Voldemort the entire time would have been a devastating reveal for the Harry Potter series. Ultimately, that's not what happened, but there's a chance J.K. Rowling might've planned to have Hagrid go bad as one of the major twists for the later books and then changed her mind despite planting the seeds for it. On top of Hagrid being better at magic than he should be and the possibility of him hiding behind a fake persona to throw people off, countless other pieces of evidence point to him being a dark wizard.

For instance, Harry Potter and the Chamber of Secrets. Hagrid is one of the many memorable characters who added to the richness of the Harry Potter series, and his characteristics were likely done to make him likable. He is also one of the first adult characters in the series to form a personal connection to Harry, but after this theory, it might've been his plan all along to get close to the Boy Who Lives as a double agent working for Voldemort. Unlikely, since this is all probably just a coincidence, but it's still fun to think about.