Severus Snape might be a character in these fanfictions. His complex relationship with both Harry and Voldemort (Tom Riddle) can add an extra layer of drama. He could be suspicious of Harry's time - traveling actions and think it might disrupt the future he has worked so hard to protect, or he could find himself in a position where he has to help Harry against Tom Riddle in the past.
Hermione Granger is often a popular character. She can use her intelligence to figure out the implications of time travel and help Harry or deal with Tom Riddle in some way. For instance, she might research spells to counteract any dark magic that Riddle tries to use during their time - traveling encounters.
Dumbledore is also frequently included. His vast knowledge and wisdom can play a crucial role. He could be the one guiding Harry from afar, even in the time - travel scenarios. Maybe he has some hidden knowledge about time travel that he imparts to Harry to help him in his encounters with Tom Riddle.
They can interact as students. For example, if they time - travel to when Tom Riddle was at Hogwarts, they could be in the same classes or clubs. Maybe they join the Duelling Club where Tom Riddle was known to participate. Another way is through chance encounters in the hallways or the library. They could strike up conversations about magic or Hogwarts history.
Tom Riddle might be very suspicious at first. He is a very intelligent and cautious person. He would likely view time travelers as a threat to his plans or as a strange new phenomenon that he wants to control. So, he could start by trying to figure out their motives and how they managed to travel through time.
Sometimes, secondary characters like Dumbledore can also be really well - written in these fanfictions. Dumbledore might be the one guiding Harry in his time - travel adventure. His wisdom and knowledge can add a lot to the story, and his relationship with both Harry and Tom can be explored in new and exciting ways.
I'm not sure if it's popular. It's a rather niche and unusual concept, so it might not have a wide following. But in the world of fanfiction, there are always small groups of people interested in unique and out - of - the - ordinary ideas.
The theme of self - discovery is also quite common. The time - traveler often discovers things about themselves, their own magic, and their place in the wizarding world while interacting with Tom Riddle. They might learn about their own family history or the true nature of their magic through the experiences in the past. This can be intertwined with the moral dilemma of whether to interfere with Tom Riddle's life or not, as it could have far - reaching consequences for the future.
Another well - liked original character is Sophia. She's a Muggle - born witch who accidentally time - travels. She has a unique perspective as she comes from a world without magic knowledge initially. When she meets Tom Riddle, she tries to show him the beauty of the Muggle world, hoping it will change his view and prevent him from hating Muggles, which is a key part of his transformation into Voldemort.
In addition to them, there could be other characters from the original 'Harry Potter' series who play important roles. For instance, Dumbledore might still be a guiding figure in Harry's life. He could be suspicious of this new friendship between Harry and Tom and try to keep an eye on them. Hermione and Ron could also be part of the story, either supporting or being skeptical of Harry's new friendship with Tom.
One character that would be great to pair with Harry and Tom is Remus Lupin. His kindness and understanding, as well as his own struggle with his werewolf side, could provide a different angle on dealing with Tom's darkness and Harry's heroism. Another good character is Bellatrix Lestrange. Although she was on Voldemort's side, her fanatical loyalty and powerful magic could make for an interesting dynamic in a fanfic where she might have to interact with Harry and a redeemed or different Tom. And of course, Ron Weasley. His friendship with Harry is well - known, and his reactions to Tom Riddle and the situations involving him could add humor and a down - to - earth element to the fanfiction.
Hermione could be a major character. She might use her intelligence to try and figure out where Tom has taken Harry. She could be researching old spells or looking through Tom's past hideouts to find clues.
I think Luna Lovegood would be an interesting character to include. Her unique perspective on magic and the world around her could add an element of mystery and wonder to the fanfiction. Also, Severus Snape. His complex past and relationship with both Harry and Tom (in a way, as Tom became Voldemort) could bring a lot of depth to the story. And Hagrid, who could provide a connection to the more gentle and nurturing side of the wizarding world, which might be important for Harry and Tom's relationship development.