Well, it could be Slenderman as the creepypasta. He's a very well - known figure in the creepypasta world. The child could be an orphan who has had a series of strange and unexplained events happen around them, which is what draws Slenderman to adopt them.
Another option could be BEN Drowned. He could come across a child who is into video games like he was when he was alive. The child might be a bit of a loner and BEN sees a bit of himself in the child. So he adopts the child in his own strange, digital way.
Maybe the child turns out to have some special power that the creepypasta was unknowingly drawn to. As the story progresses, the creepypasta realizes that adopting the child has put both of them in danger as there are others who want to use the child's power for their own evil purposes.
Sakura's family members could play important roles. Her parents could initially be hesitant about her decision to adopt but later come around and become loving grandparents to the adopted child. Also, there could be other ninja in the village. For example, Hinata could be a character. She might become friends with the adopted child and help Sakura with things like cooking for the child or teaching the child some basic self - defense moves.
It could be an orphaned wizard child from a family that was killed by Death Eaters. This would give Snape an added sense of responsibility as he might feel guilty for being associated with the Death Eaters in the past.
The child could be an orphan from a small, destroyed village that Naruto comes across during one of his missions. This child might have lost their family to a powerful enemy and Naruto feels a sense of responsibility to take them in.
It could be a young wizard who lost their parents during the final battle against Voldemort. Harry feels responsible for all the orphans created by the war and decides to take this particular child under his wing.
Edward could be an ordinary man living in a small town. He has always wanted a family of his own but couldn't find the right partner. So, he decides to adopt a child to start his own family unit.
Perhaps the child is the offspring of a Titan. This would make for an interesting story as Percy would have to deal with the potential danger and mistrust from other demigods. But Percy, being Percy, would see the good in the child and adopt them regardless. The child might have unique powers that set them apart from other demigods, like the ability to control time or space.
Squirtle. Squirtle is cute and friendly. If it adopted a human child, it could show the child the underwater world of Pokemon. The Squirtle could teach the child how to swim, and they could explore underwater caves together. It would be a really fun and light - hearted story with Squirtle as the main Pokemon.
Harry could be the same Harry Potter we know from the books, a brave and kind - hearted wizard. Kara could be a character from another universe, perhaps with superhuman abilities like flying or super strength. Maybe she's an alien like Supergirl Kara, but in this fanfiction, she's in a situation where she needs to be adopted by Harry.
Twilight Sparkle could be a main character. Since she is very intelligent and curious, she might be the one who gets drawn into the Creepypasta - related events. Her knowledge of magic could also play a crucial role in either solving the problems caused by the crossover or in getting trapped in the first place.