https://en.wikipedia.org/wiki/Legal_disputes_over_the_Harry_Potter_series

There’s a lot of gray area in the whole Young Adult Fantasy Wizard space. Case in point:

In June 2009, the estate of Adrian Jacobs, a children’s author who died in 1997, sued Rowling’s publishers, Bloomsbury, for £500 million, accusing her of having plagiarised “substantial parts” of his work in writing the novel Harry Potter and the Goblet of Fire. In a statement, Jacobs’s family claimed that a scene in Goblet of Fire was substantially similar to Jacobs’s book The Adventures of Willy the Wizard: Livid Land.

Both Willy and Harry are required to work out the exact nature of the main task of the contest which they both achieve in a bathroom assisted by clues from helpers, in order to discover how to rescue human hostages imprisoned by a community of half-human, half-animal fantasy creatures

Is it possible that Rowling (or one of her ghostwriters) lifted passages from another Wizard Adventure novel with a similar theme of deadly puzzle games? Certainly. Is it possible that there’s simply some overlap in how a couple of authors with relatively limited creativity can compose a cliche of the genre? Also certainly.

There’s not any material evidence to suggest Rowling straight copypasta’d text from a prior copywritten work. But that would be devilishly hard to come by. As it stands, I’m open to the theory that Rowling’s writing team cut corners by pulling a bunch of low-circulation published works and mining them for ideas. But I have relatively little confidence in their ability to prove any of it.