Maybe the story could revolve around how Harry and Luna protect their baby from dark forces that still lurk in the wizarding world. They would use their unique skills and knowledge to keep the baby safe. For example, Luna's ability to see things others can't might help them detect hidden threats. Harry, with his combat skills, would be ready to fight off any attackers. Their friends like Ron and Hermione could also play important roles in this story, perhaps helping to babysit or providing magical protection for the baby.
One possible plot could be Harry starting to share Luna's unique views on magical creatures. For example, he might start believing in the existence of some of the more obscure creatures Luna is fond of, like the Crumple - Horned Snorkack. This could lead to him going on adventures to find evidence of these creatures, much like Luna would do.
Well, one plot could be that Harry is adopted by a family outside of the wizarding world. He grows up with no knowledge of magic until strange things start to happen around him. Then he discovers his true heritage.
One possible plot could be Luna being overly possessive of Harry in a way that surprises him. For example, she might try to keep him away from his other friends at Hogwarts, thinking they are a bad influence on him. Another plot could be Luna using her unique magical abilities in rather extreme ways to protect Harry from perceived threats.
Well, perhaps in the fanfiction, Snape discovers Harry has a special magical ability that is both a danger and a great potential. As a 'daddy' figure, he has to guide Harry in controlling it without alerting the wrong people. He might take Harry on secret excursions to practice this ability in safe places.
Well, in this type of fanfiction, a plot could be that Harry is forced to be a baby due to a dark magic experiment gone wrong. As a baby, he may start to show signs of his future heroic self in unexpected ways. For instance, he might be able to communicate with magical creatures that are drawn to his innocent form. Also, Dumbledore could be faced with a new challenge of protecting Harry in this vulnerable state. He might have to place Harry in a different kind of hiding, perhaps with a family that has special abilities to deal with magically altered children.
One interesting plot could be their first encounter as babies and how they seem to have an instant connection, like they recognize something special in each other. Maybe they reach for each other's hands or stare at each other in a really cute way.
Perhaps a plot where Ash and Luna enter a mysterious Pokemon tournament that has never been heard of before. In this tournament, they encounter unique Pokemon and battle strategies that test their skills to the limit. As they progress, they also learn more about each other's pasts and how they came to love Pokemon.
Well, one interesting plot could be the baby showing early signs of magic. Maybe the baby accidentally makes toys float around the nursery, causing both Harry and Ginny to be both amazed and a bit worried about how to handle this early display of magic. Another plot could be the baby's first encounter with the Weasley family as a whole. All the aunts and uncles would be fussing over the little one, and there could be some really heartwarming and funny moments.
One plot could be that in a dark version, Harry and Luna team up to expose a hidden, evil regime within the wizarding world that has been secretly controlling things from the shadows. They might have to use some rather unorthodox and darker magic to do so.
One possible plot could be Baby and Deborah going on a cross - country adventure, with Baby's amazing driving skills coming in handy during various unexpected situations, like escaping from some bad guys who are after them for some mysterious reason.