It could be the Queen of England, as in the real - world monarchy. In the fanfiction, she might be a figure with hidden knowledge of the wizarding world and decides to use her power to rescue Harry.
Well, in this kind of fanfiction, perhaps the Queen uses her power and resources to rescue Harry Potter from a dangerous situation. Maybe he's trapped in a dark wizard's lair and the Queen arrives with her guards to save him.
In the fanfiction world, Greengrass is often a Slytherin student. She usually comes from a pure - blood family, which gives her certain status and expectations within the wizarding world. In the context of rescuing Harry Potter, she might be a character with a strong sense of justice that goes against the typical Slytherin stereotype. She could have her own set of skills, like being an excellent duellist or having a deep understanding of certain types of magic that enable her to come to Harry's aid.
In this fanfiction, Harry Potter would interact with the Queen in a very unique way. Since he is used to the hierarchical system in Hogwarts, he would understand the importance of showing deference to the Queen. He could offer her a magical gift, like a charm that gives good luck. And the Queen, being curious, might ask him about his world. Harry would have to be careful not to reveal too much about the wizarding world to the muggles, but still satisfy her curiosity. There could be some misunderstandings too, for example, when Harry tries to explain some magic concepts using wizarding terms that the Queen doesn't understand.
Well, it could be that the Queen has a special connection to the wizarding world in this fanfiction. Perhaps she has been secretly informed of Harry's bravery and selflessness all along. And as a symbol of the British monarchy, she knights him to show that the Muggle and wizarding worlds can have a positive relationship. So, she bestows this honor on Harry.
It could be an original character created specifically for the fanfiction. A young and beautiful queen of a small, yet prosperous kingdom, who has a strong will and a love for her people. She might be open - minded and curious about the wizarding world, which makes her a perfect match for Harry.
It might be an ancient magical being that has the form of a queen. She could have ties to the very origins of magic in the Harry Potter universe and decides to save Harry because she foresees his importance in the future of magic. For example, she could be a guardian of some sort of magic that is crucial for Harry to defeat Voldemort in the long run.
One common theme is the clash of different worlds. For example, when Harry Potter is rescued in a crossover with another universe, like the Star Wars universe, there's a lot of focus on how the magic of Harry's world interacts with the technology and different species in Star Wars. It's about two very different concepts trying to coexist.
One possible plot could be that Harry is wrongly accused of a crime in the wizarding world, perhaps something related to dark magic. The police, who might be a new magical law enforcement unit, rescue him from an angry mob. They then help him clear his name by finding the real culprit, who could be a Death Eater in disguise trying to frame Harry to cause chaos in the post - Voldemort era.
Perhaps there is a prophecy in both universes that foretells of a great danger that only the combined forces of Harry Potter and the Avengers can face. When the Avengers learn of this, they travel to the wizarding world to find Harry. They rescue him from an immediate threat so that they can all prepare to face this greater danger together. The Avengers could introduce new ways of fighting and thinking to Harry, while Harry could share his knowledge of magic with them.