Continuity: In Quidditch Through the Ages, it says that the first ever World Cup was in 1473, with a match being held every 4 years. Yet the World Cup in 1994 is number 422. There can't be 422 world cups in 521 years with a four-year gap in between. Calculated correctly, the World Cup that the Weasleys, Hermione, and Harry attend is actually the 131st, and it should have been held in 1993.

Factual error: In Hogsmeade, Sirius implies that at a certain point, Snape's attendance at Hogwarts overlapped with Bellatrix Lestrange's. But given their dates of birth, Bellatrix would have left school two years before Snape started.

Continuity: When Fred and George bet on the Quidditch match with Bagman, it says Fred put the paper with their wages in his robes, but Fred was wearing Muggle clothing.

Other: In one scene, Molly Weasley reminisces about the gamekeeper before Hagrid, named Ogg. But in other books, it is implied that Hagrid has held that post since his expulsion from school in 1943. Since Hagrid's years as gamekeeper appear to overlap Molly's years at school, it seems unlikely that she knew a previous one.

Continuity: During Priori Incantatem, Voldemort's victims come out in reverse order. However, James comes out before Lily. He should come out last, because he was killed before Lily. (Corrected in later versions of the book).

Factual error: Harry says to Sirius in one of his letters that Dudley chucked his Playstation out the window. However, Book 4 takes place in 1994, and the PlayStation wasn't launched in Britain until 1995.

Continuity: When Dumbledore, Fudge, and Moody are talking about Crouch, at one point it says, "said Crouch angrily." Crouch wasn't in the room – they were only talking about him.

Plot hole: Harry is entered into the Triwizard Tournament under the name of a false school. Since Dumbledore asked potential champions to write the name of their school on their entries, he should have noticed the fake school on the parchment with Harry's name. In addition, Dumbledore wasn't the one who was Confunded, so he still knows that only three schools participate.

Continuity: When Sirius visits Harry, Ron, and Hermione in Hogsmeade, he mentions that they and Professor Dumbledore are the only people around the village who know he is an Animagus. But Professor Snape knows this, as well.

Continuity: In chapter 35, the book says '"The Imperius Curse," Moody said.' However, the Polyjuice Potion has already worn off, so it should be Barty Crouch Jr. speaking.

Continuity: In the beginning, it says that Harry thought that for one hour last year he'd be staying with Sirius, but in the third book, he only thought he'd be staying with Sirius for a half an hour.

Continuity: When Moody demonstrates the Imperius Curse, the book says he used it on Harry four times. However, later in the book, it says "And Harry felt, for the third time in his life, the sensation that his mind had been wiped of all thought." It should be the fifth time because he had already experienced the Imperius Curse four times before.

Continuity: In chapter 28, Harry says that the password to Dumbledore's office two years ago was "sherbet lemon", but the password that Professor McGonagall actually used in book 2 (chapter 11) was "lemon drop".