Like any great fantasy or sci-fi series, Harry Potter is full of Easter eggs, the subtle references that turn us all into giggling nerds.
The Easter egg we are referring too relates to the lead character of Fantastic Beasts and Where to Find Them, Newt Scamander.
Long before the release of the film in 2016, Scamander had already appeared in the Potter cinematic universe in a 'blink and you'll miss it' moment.
In Harry Potter and the Prisoner of Azkaban (both the best book and the best film, in this writer's opinion), Scamander, an author of textbooks in the mythology is shown on the magical Marauders Map, given to Harry by the Weasley twins.
Sadly it's not Eddie Redmayne, but just a name tag that is shown wondering the halls of Hogwarts at that time on the map.
Attentive Potter fans have been noticing this for a number of years now but it's only since the release of Fantastic Beasts that it has gained more notoriety.
Given that a Fantastic Beasts and Where to Find Them book was only published in 2001 and Prison of Azakaban, the film, was released in 2004 it's possible that this was only a fun little nod to fans.
However, it hasn't stopped people compiling their own theories as to why Newt was in the hallowed halls of Hogwarts on that day.
The first theory involves the possible friendship between Newt and Dumbledore.
The headmaster of Hogwarts taught Newt as a student and had also wrote the fictional forward for his textbook so it's possible he was just visiting a friend.
Another suggestions points us in the direction of Buckbeak, the hippogriff, formerly owned by Hagrid.
The creature was due to be executed during the events of Prisoner of Azkaban after attacking the insufferable Draco Malfoy.
Buckbeak is eventually saved and freed by Harry and Hermoine, therefore it's possible that Dumbledore contacted his old student, who is an expert in magical creatures to care for the animal.
Or something like that.
Either way, we'll probably never discover the true answer so just appreciate it fun the fun little reference it is.