Celebrity screen tests: Watch the stars try out for their most famous roles

Imagine if Rachel McAdams hadn't auditioned to play Allie? (NEVER!)

As hard as it is to imagine Blake Lively not playing Serena van der Woodsen, or Rachel McAdams not taking on the role of Allie Calhoun, Blake and Rachel, just like many stars before them, had to actually audition for their roles. Unbelievable, right?

And it pulls on our heartstrings a little bit to see these characters, now such a big part of our lives, just beginning to form, before taking on the world and being immortalised on the silver screen.

Whether Russell Brand ad-libbing as the hilarious Aldous Snow, or Lindsay Lohan taking on the casting directors at the ripe old age of ten, these expert auditions are what any inspiring actor or actress should look to before attempting to win a role.

Here are some of our favourites...

Emilia Clarke, as Daenerys Targaryen, Game of Thrones

While she says there's no video footage of her GOT audition (yeah, right), Emilia Clarke telling the story of how a sugar high made her do something very... un-Daenerys, is absolutely hilarious.

Rachel McAdams as Allie Calhoun, The Notebook

The Notebook is the quintessential romantic tearjerker - and they couldn't have given the role to anyone else after Rachel stole the show with this emotional audition. I mean, you're watching Allie and Noah - those two were made for those parts.

Alyson Hannigan as Michelle Flaherty, American Pie

Miley Cyrus as Hannah Montana, Hannah Montana

Selena Gomez as Alex Russo, Wizards of Waverly Place

Steve Carell as Brick Tamland, Anchorman

Blake Lively as Serena van der Woodsen, Gossip Girl

Gabourey Sidibe as Precious, Precious

Natalie Portman as Mathilda Lando, Leon: The Professional

Scarlett Johansson as Judy Shephard, Jumanji

Kate Winslet as Rose Dawson, Titanic

Emma Watson, Daniel Radcliffe and Rupert Grint as Hermione, Harry and Ron, Harry Potter and the Philosopher's Stone

Lindsay Lohan as Annie James and Hallie Parker, The Parent Trap

Russell Brand as Aldous Snow, Forgetting Sarah Marshall

Daisy Ridley as Rey, Star Wars: The Force Awakens

Before being cast in the third biggest film of all time, Daisy was an unknown British actress starring in minor television roles. This powerful audition clinched her the role of Rey shooting her to international fame.

Which one's your favourite? Tweet us @marieclaireuk