Perhaps it involves Teddy showing Harry some new magical abilities or spells that are not common knowledge. Since Teddy is a teen, he might have a different perspective on magic compared to young Harry. They could also get into some sort of adventure outside of Hogwarts, like exploring an ancient wizarding ruin together.
Well, it could be about Harry Potter, in his younger days, stumbling upon a teen Teddy. Maybe they team up to face some sort of magical mystery in Hogwarts. For example, they might find a strange enchanted object that's causing chaos in the school and they have to figure out how to stop it.
The plot might revolve around their friendship development. Young Harry, who has had his own share of difficulties, might find a kindred spirit in teen Teddy. They could start off not getting along very well, but as they face challenges together, they learn to trust and rely on each other, eventually becoming great friends and allies in the wizarding world.
There could also be other supporting characters. For instance, some of Harry's friends from Hogwarts like Ron and Hermione might make an appearance. They could be skeptical of Teddy at first or be involved in the adventures that Harry and Teddy go on. Also, Teddy's family or friends might be mentioned or even play a small part in the story, which could add more depth to his character.
Well, perhaps in the fanfiction, Harry adopts Teddy Lupin right after the Battle of Hogwarts. Teddy is just a baby then. Harry, who has lost so many people, sees Teddy as a new beginning. He might face challenges from the wizarding community as some may question his ability to raise Teddy. But Harry, with the help of his friends like Hermione and Ron, overcomes these difficulties and Teddy grows up to be a strong and kind wizard.
One possible plot could be that Harry, through some time - traveling magic, meets young Severus. Harry, knowing Severus' future, tries to befriend him and change his path. He could introduce Severus to different ways of using magic that are less dark - oriented, which might change Severus' perception of magic and his future relationships in Hogwarts.
Well, it could be about Teddy Lupin traveling back in time and meeting his father's friends, the Marauders. Maybe he gets to experience their pranks first - hand and learns some new magical tricks from them.
Another possibility is that there is some sort of magical imbalance that only Harry and the Morrigan together can fix. Harry's knowledge of the wizarding world and the Morrigan's ancient and powerful magic combine to face a great evil that threatens both of their worlds. Harry has to learn to trust the Morrigan, even though she is a very different kind of magical being from what he has known.
Well, perhaps Harry Potter could accidentally stumble into the world of Tinkerbell. He might be on one of his adventures in the Forbidden Forest and find a magical portal. Once in Pixie Hollow, Harry could use his magic skills to help Tinkerbell and her friends solve a problem like a dark force threatening their home. He could teach them some new spells while they teach him about the magic of their world.
Perhaps the plot involves a magical artifact that has fallen into the wrong hands in the Supernatural world. Harry, with his knowledge of magic, and the Winchesters, with their experience in dealing with the supernatural, set out to retrieve it. They might face all sorts of challenges along the way, from vampires and werewolves to dark magic spells.
Well, perhaps Teddy is in some sort of danger. Maybe he's being targeted by dark wizards because of his connection to Harry. Harry, being the heroic type, decides to fight to protect Teddy. He could use his magic skills and the support of his friends like Hermione and Ron to keep Teddy safe.
Well, perhaps in the fanfiction, Harry adopts Teddy after Teddy has some trouble at Hogwarts. Harry steps in as a father figure. He teaches Teddy advanced magic, things he learned from his own adventures. They might also have a trip around the world of magic together, visiting different magical communities and learning about diverse magic cultures.
In this kind of fanfiction, perhaps Teddy Lupin discovers a magical way to time - travel and meets his father. It could show Teddy learning about his father's character and values through their interactions. Maybe his father teaches him some unique magic that was passed down in the family.