|"Is this all real? Or has this been happening inside my head?"
The topic of this article is of a real-life subject 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.
In 1812, they published Children's and Household Tales, a collection of German fairy tales they had gathered. Among the stories it contained were "Cinderella" and "Snow White and the Seven Dwarves". These became favourites of Muggle children but remained relatively unknown among wizarding families. However, the Hogwarts library kept at least one copy of Household Stories, an English translation of the tales by Lucy Crane.