One common plot element is Harry's struggle with loneliness. Since he's immortal, he'll outlive all his friends and loved ones, which can lead to a sense of isolation.
One common plot element is the idea of Harry Potter having some form of immortality and then getting involved in the world of Hobbits. Maybe he uses his magic to help the Hobbits in some way, like protecting them from a new dark force.
A plot twist might be that Harry's immortality is the key to saving the Twilight world from a new, unknown threat. He might be the only one who can stop it because his magical immortality gives him abilities that the Twilight creatures don't have. Also, there could be a love triangle or some sort of complex relationship where Harry falls in love with a character from the Twilight series, but there are obstacles because of his different nature and the fact that he's from another world. And sometimes, the magic in the Twilight world is revealed to be related to the magic in Harry Potter's world in a way that no one suspected before.
False accusations are very common. Usually, Harry is wrongly blamed for something he didn't do, like being involved in dark magic activities.
One interesting plot element is the clash of magic systems. In Supernatural, magic is often more about spells and rituals from a hunter's perspective, while in Harry Potter, it's about wand - based magic. When these two meet, it creates a really unique dynamic. For example, seeing Sam try to figure out how to use a wand or Harry trying to understand the more ancient forms of magic the Winchesters use.
The themes in 'Harry Potter is immortal' fanfictions usually include a search for purpose. Harry has an endless life, so he needs to find something meaningful to do. There is also the theme of change. While he doesn't age, the world around him does, and he has to adapt. And of course, the theme of mortality in contrast to his immortality. He is constantly reminded of the fact that everyone else is mortal, and this can create a lot of internal conflict within him.
Another element could be the interaction between the wizarding world and the Muggle world of cars. Harry might have to hide his magic while fixing cars in the Muggle world, or he could introduce some magical car features that amaze the Muggles. In some fics, there could be a conflict when other wizards don't approve of Harry using magic in such a Muggle - oriented way. This adds drama and tension to the story.
Well, often there will be a focus on Harry having to keep his true identity a secret even from his friends. There could be a lot of cloak - and - dagger type situations where he has to meet with double agents or decode mysterious messages. Also, his skills in Potions and Transfiguration might be used in a more espionage - related way, like creating potions to make people tell the truth or transfiguring objects into spying devices.
One common plot element could be the dog causing disruption. For example, it might run amok in Hogwarts, knocking over potions and scaring first - year students. Another could be the dog having a hidden power or connection to the wizarding world's secrets. Maybe it's the key to unlocking an ancient spell or a hidden chamber. And often, the main characters like Harry Potter would have to either tame the dog or figure out its mystery.
Well, one common element is the use of magic in a strategic way. For example, in many such fanfictions, characters will use spells like the Disillusionment Charm to hide and then suddenly reveal themselves to surprise their 'prey'.
One common plot element is the discovery of the heir. It often involves a young wizard or witch suddenly realizing they have a connection to Grindelwald. Another is the struggle with the dark legacy. The heir may be conflicted about whether to embrace the power associated with Grindelwald or reject it. And there's usually some sort of conflict with the existing wizarding community, as they may be feared or mistrusted.