If you've seen the new sequel to Disney's Mary Poppins (Mary Poppins Returns), then you'll probably remember the bathroom scene where Mary transports herself and the Banks children to a magical underwater world...
A video has gone viral online showing just how the film crew created the iconic scene.
While most people assumed Mary disappeared down the bath using computer generated effects - it actually turns out that actress Emily Blunt slid down a physical slide...
Fans were pretty shocked when they realised the lengths the film went to.
You can watch a trailer for the new film below...
