J.K. Rowling Originally Wrote Harry Potter's Hogwarts Houses Idea On An Unusual Item

Harry Potter author J.K. Rowling says she first wrote the idea of the Hogwarts houses on an airplane vomit bag. Rowling shared the anecdote on Twitter.

The best thing I ever wrote on was an aeroplane sick bag. Came up with the Hogwarts houses on it. https://t.co/Fut4BvS6iM

— J.K. Rowling (@jk_rowling) December 15, 2017

"The best thing I ever wrote on was an aeroplane sick bag," Rowling revealed. "Came up with the Hogwarts houses on it."

Rowling's tweet came in response to The Woman in Cabin 10 author Ruth Ware, who recalled a time she recorded notes on a napkin during a birthday party.

Among the novel series' most famous creations is the concept of four houses belonging to the Hogwarts School of Witchcraft and Wizardry, the magical school attended by young wizard Harry Potter and best friends Hermione Granger and Ron Weasley.

Upon arrival to the school, the mystical Sorting Hat assigns first years to one of four houses — Gryffindor, Hufflepuff, Ravenclaw and Slytherin — which often hint at the true nature of its members.

The famed author recently found herself making headlines for her defense of Johnny Depp's casting in the Fantastic Beasts franchise, a spinoff and prequel of the Harry Potter saga. Depp came under fire in light of domestic abuse allegations made by his ex-wife, Aquaman star Amber Heard.

A biopic based on Rowling's life is gaining traction in Hollywood. When Lightning Strikes tells the story of Rowling weathering "first loves, unexpected pregnancies, lost jobs, and depression on her journey to create Harry Potter."

The Harry Potter creator is not involved in the as-of-yet unproduced screenplay. Rowling scripted Fantastic Beasts sequel The Crimes of Grindelwald, opening November 16, 2018.