You may find this hard to believe but even the greatest actors ever to grace the silver screen have had to appease a panal of expert Casting Directors and cross their fingers in the hope they can land that once in a lifetime role.
With any interview/audition is the invitation of pressure into the room. Pressure can be a great thing as it can be utilised for adrenaline and the sharpening of your senses for the all-important moment or it can cause you to crumble to the ground and wish you were anywhere else, but that spot.
It's vital that a casting director sees the actor at their apex and to do that they are required to ask unusual things of a performer to extract their ability. Sometimes the Casting Director/Director do this by being plain difficult or they can offer the stage for an actor to improvise.
Singing 'Pure Imagination' whilst pretending to be an oil slick seems like a walk in the park compared to what these actors were put through... here's 10 Auditions you would NOT believe.