|"Is this all real? Or has this been happening inside my head?"
The subject of this article is of a real-life person, place, group, company, product, or creative work that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really exists), and, as such, details contained in this article may differ from real world facts.
When Severus Snape subsituted for Remus Lupin for a short while in teaching Defence Against the Dark Arts during the 1993–1994 school year, he claimed that Kappas were primarily found in Mongolia. However, Fantastic Beasts and Where to Find Them states that Kappas are from Japan, a fact Harry Potter made note of in his copy of the book.