Definitely Harry Potter himself. He's the central character in his own series, so it's likely he'd be involved in any crossover. Hermione Granger could also be a key character as she's smart and curious, and would be interested in learning about the 'Twilight' world. From 'Twilight', Edward Cullen is an obvious choice. His brooding nature and unique abilities would make for interesting interactions with the 'Harry Potter' characters. Also, Jacob Black could be involved, especially when it comes to the 'imprint' aspect as he has his own story arc related to that in 'Twilight'.
In this kind of fanfiction, Severus Snape could be an interesting character to be involved. His complex personality and his knowledge of the dark arts in 'Harry Potter' could lead to some intense interactions with the vampires in 'Twilight'. From 'Twilight', Bella Swan could be included. Her connection to both the vampire and werewolf worlds in her own story could translate well into the crossover. And then there's Ginny Weasley. She's brave and strong - willed, and could potentially have some interesting relationships with the 'Twilight' characters, especially when considering the 'imprint' concept.
Voldemort would also be a key character. His obsession with immortality and his actions that led to many deaths in the series are fundamental to the theme of life and death. In a crossover, he could be pitted against new threats or forces that have different views on death, which would make for an interesting story.
Definitely the Weasley twins, Fred and George. They are known for their love of mischief and innovation. They would be all over the idea of street racing in the wizarding world. They could create all sorts of magical gadgets to use during the races. Another character could be Draco Malfoy. He would likely be a rival racer, using his family's wealth and influence to get the best magical racing equipment.
Harry himself is very likely to be involved. Given his many encounters with death, from facing Voldemort to losing loved ones, he has a deep connection to the concept. He would be exploring the aspect of death perhaps to gain more power to protect his friends and the wizarding world.
Edward Cullen and Harry Potter are often popular. The contrast between Edward's vampire nature and Harry's wizardry makes for an interesting dynamic. Fans like to imagine how they would react to each other's powers and the situations they face.
Homer Simpson is very likely to be involved. He's the main character and his bumbling yet loveable nature can create a lot of comical situations in crossovers. For instance, if it's a crossover with 'The Flintstones', Homer would probably be trying to out - eat Fred Flintstone at the local diner.
Definitely Edward would be one of the likely characters. His intense love for Bella in the original series could easily be translated into an imprint situation. Jacob is also a strong contender as he has his own deep connection with Bella. Additionally, if we consider other supernatural beings from the Twilight universe, perhaps a Volturi member could be involved. The Volturi are known for their power and mystery, and if one of them were to imprint on Bella along with either Edward or Jacob, it would create a very interesting power dynamic. There could also be a new werewolf pack member that Bella meets and who imprints on her along with someone else.
Harry Potter and Nate Ford could be a likely pair. Harry's experience with facing great evils and his leadership skills combined with Nate's strategic mind in planning heists would make for an interesting dynamic. They could learn from each other's methods of problem - solving.
Caleb Prior from Divergent and Ron Weasley might be a crossover. Caleb is intelligent but has his own moral dilemmas, and Ron is a loyal friend with his own insecurities. Their friendship or conflict could be explored in the fanfiction, perhaps with Caleb getting involved in Ron's wizarding adventures and Ron learning about the Divergent world through Caleb.
Well, for sure Harry Potter is a top pick. His connection to Gringotts started early on when he first visited to get his inheritance. Hermione would be there as she's the brains of the group and would be curious about any magical lore associated with Gringotts. Ron, with his family's financial struggles, could also play an important role. The goblin bankers are a given as they are the heart of Gringotts. In terms of crossover characters, if it was a crossover with 'Alice in Wonderland', the Cheshire Cat could make an appearance. It could be lured by the shiny objects in Gringotts and cause some chaos as it tries to steal something, with Harry and his friends having to stop it.
Obviously, Harry, Hermione and Ron are the most likely. They are the main characters and are always together, so it's natural for them to be playing truth or dare. Neville could also be involved as he's their friend. And Ginny might join in too, especially as she gets older and becomes closer to the group.