With any franchise as full as Harry Potter, there are bound to be inconsistencies that come up. JK Rowling may have created one of the best fantasy universes to date (one of, mind) but even so, there is always room for error.
You might find it hard to believe, then, that the movie adaptations of her novels actually solved a problem Rowling created herself. Of course, the solution created more problems later, but Harry Potter director David Yates didn't know it at the time.
In the Order of the Phoenix novel, JK Rowling introduced another magical object to the canon: a two-way mirror that allows communication between its owners. The book had Sirius give Harry the mirror after Christmas break and urged him to use it if Snape was giving him a hard time.
Related: How to watch every Harry Potter movie online now
It seems, however, that Harry forgot about the gift altogether, and after Snape gave him a hard time, Harry instead used the Floo Network to contact his godfather. That he forgot about the gift is one thing, but that Sirius did is another.
The Floo Network is notoriously unreliable. Anyone hiding in the room could overhear, or simply take over the conversation by sticking their head into the fireplace. Besides which, it necessitates the person you want to talk to being at home.
Luckily for Harry, Sirius was – though it was Remus who 'answered' the Floo call and subsequently went to fetch Sirius. Instead of Sirius asking Harry why he didn't use the mirror, he instead launched into a comforting speech.
Had Sirius said, 'Hey Harry, why didn't you use the gift I gave you?', then later on Harry might have remembered its existence. Then Kreacher lying to Harry wouldn't have happened, Harry would have been able to confirm Sirius was safe and not dragged everyone to the Ministry of Magic and to their deaths.
So, it's no surprise that when it came time to shoot the film, Yates and screenwriter Michael Goldenberg opted not to include it. The movies are already full of little details and omitting a mirror might not have seemed like the biggest deal.
It did two things – firstly, it solved the problem of Sirius not reminding Harry about the mirror. Secondly, though, it opened up an even bigger plot hole in future films.
Unknown to them, the mirror would become integral to Harry's story in Harry Potter and the Deathly Hallows, which would be split into two films. As a result, the shard of glass from the mirror is introduced into the film with almost no explanation whatsoever.
Granted, there are many other plot holes in the movies that have nothing to do with the books, but it's rare when a film actually solves a problem in its source material.
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