Building 9¾ from Harry Potter

On the night of the release of the movie Harry Potter and the Goblet of Fire, Building 9 was turned into Building 9¾. Doors, classrooms, and bathrooms throughout the building were relabelled to represent rooms in Hogwarts, the School of Witchcraft and Wizardry in Harry Potter stories.

The number "9¾" comes from the number of the train platform used for getting to Hogwarts.

Some offices were relabelled to the names of professors from the series (such as Quirrell, McGonagall, Moody, Flitwick, and Snape.

Bathrooms were relabelled to be for "Wizards" and "Witches", as appropriate.

Some classrooms and lecture halls (and even the mail room) were also renamed.