Most actors will tell you that auditions have the capacity to be quite an intimidating environment.
Being sat in front of a panel of executives and creatives who have the power to make or break your career is pressure enough, but to then add the unpredictable beast of performance to that mix is bordering on cruel.
That immense pressure isn't exclusive to live auditions either, as many actors put themselves through the ringer in order to make sure a self-taped audition is up to scratch, too.
So imagine having the guts - when faced with all of those combustible variables - to pull something out of the air and try a line or character trait that hasn't been put in a script for you to prepare.
Anyone who has attempted to improvise in front an audience will tell you that it can very quickly backfire, if you don't have faith in what you're about to do. Yet, guts translated into glory for this talented bunch and their sporadic moment of brilliance managed to bag them that all important role.
Who knew that winging it could be so effective?
10. Chris Pratt - Guardians Of The Galaxy
Chris Pratt is yet another star who rose to prominence as a comedy actor, most notably providing a laugh-a-minute as Andy Dwyer in Parks and Recreation (2009-2015). He would eventually go on to shed that image, transforming into the quick-witted action star we know today.
Yet, that's not to say that his excellent timing and adept ability to improvise didn't aid him in his quest to break into the upper echelon of Hollywood movie stars, as his screen test for 2014's Guardians of the Galaxy captured perfectly.
Standing opposite the hulking Dave Bautista (in full Drax the Destroyer guise) a slick Pratt was tasked with convincing the brute not to kill Gamora, using the promise of sweet revenge on Ronan the Accuser as a bargaining tool.
Proving to be as perfect a fit for Peter Quill as any man alive, Pratt demonstrated how Drax could slice Ronan's throat by drawing his own finger across his neck. An uber literal Bautista questioned why he would put his finger on his throat and a hilariously improvised attempt to accommodate the dead-pan anti-hero would ensue.
If that moment wasn't enough, when Pratt decided to touch Bautista's shoulder - something Drax didn't appreciate - his subsequent quip of that being the last time he did so, encapsulated Star Lord like few others could have.
The studio executives seemed to agree and this hilarious moment even found its way into the finished feature.