A third theme could be self - discovery. Through the process of raising his child alone, Harry discovers new aspects of himself. He might learn that he has more patience or that he can be a better cook (using magic of course) than he thought, which helps him grow as a person and as a father.
One common theme is sacrifice. Harry often has to sacrifice his own desires or time for his child. For instance, he might give up on a dangerous but exciting adventure to be there for his kid's first day at Hogwarts.
Another theme is the power of love. Despite being a single father, his love for his child gives him the strength to face any difficulties, whether it's dealing with dark wizards or just the normal problems of raising a child in the wizarding world.
One common theme is the struggle of balancing the magical and non - magical worlds. Harry wants his daughter to be part of the wizarding world but also understand the Muggle world. Another theme is protection. He has to protect his daughter from dark forces that might be interested in her because of her relation to him. And there's also the theme of family, as Harry tries to create a loving family environment for his daughter on his own.
One common theme is sacrifice. James has to sacrifice his own desires and time to focus on raising Harry alone. Another theme is love. His love for Harry is unconditional and drives him to do whatever it takes to protect and raise him well.
One common theme is mystery. Since it's just a single night, there could be a lot of unknown things happening. For example, a character might discover a secret passage in Hogwarts during one night. Another theme is friendship. Friends could support each other through a difficult or exciting single night. For instance, Ron and Harry helping each other during a spooky night in the Forbidden Forest.
Another theme is the growth of the relationship between Harry and his child. Often, at the start, there are difficulties due to the absence of a second parent, but as the story progresses, they develop a strong bond. For example, in some fanfics, they start to understand each other better through shared hobbies or experiences. And this bond becomes the core of the story.
One common theme is the struggle of balancing ninja duties and fatherhood. Naruto has to be out there protecting the village but also be there for his child.
One common theme is redemption. Draco is often shown trying to atone for his past actions by being a good father. Another theme is the struggle against prejudice. People in the wizarding world may still have a negative view of him, but he has to rise above it for his child.
There is also the theme of overcoming challenges. Percy as a single father has to face various difficulties, such as financial problems if his partner was the main earner before, or dealing with the child's emotional problems due to the absence of one parent. These fanfictions often show how he overcomes these challenges with determination and love for his child.
One common theme is sacrifice. Tony often has to sacrifice his time as Iron Man to be there for his child. For example, in many fics, he misses important Avengers meetings because his child is sick or has a school event.
One common theme is the struggle to balance the demigod world and normal parenting. Percy has to protect his child from mythological threats while also ensuring they have a normal childhood like going to school, making friends. Another theme is the passing on of values. Since Percy has his own set of values from his own adventures, he tries to pass those on to his child. And there's often the theme of loneliness too. Being a single father in a world where most people don't understand the demigod situation can be isolating.
One common theme is the struggle of single parenting. Naruto has to handle all the responsibilities of raising a child alone, like providing for them, protecting them, and teaching them right from wrong. Another theme is the clash of different worlds. Since it's a crossover, there are elements from different anime universes that Naruto has to deal with while raising his child.