The Test: Garland was cast, then ditched, from Valley Of The Dolls the year before her untimely death. This test captures her during that troubled time.
Magic Moment: The actress gets a fit of the giggles.
The Test: Not every actor gets the part...even if they're famous. Alba tries out for the role that eventually went to Anne Hathaway in Get Smart .
Magic Moment: Alba doesn't even come close to making contact with her co-star with a half-hearted punch. Sometimes, it's worth putting the whole effort in.
The Test: Back when he was still a serious actor, Nielsen was up for Messala, the lead villain role in Ben Hur (although, given that Nielsen's back is to the camera, this test is for the other actor).
Magic Moment: Nielsen shows off his spear-throwing prowess.
The Test: A wordless test for The Fifth Element , which highlights the extent to which Luc Besson chose Jovovich based on her statuesque, athletic on-screen presence.
Magic Moment: Leeloo's ethereal innocence shines through as Jovovich stretches out her arms.
The Test: Depp goes Chaplin-esque in these technical tests for Benny And Joon .
Magic Moment: The crazed smile Depp cracks after completing his Gold Rush -riffing dance of the bread rolls.
James Dean, Natalie Wood and Sal Mineo
The Test: Not strictly a screentest as all three had already been cast in Rebel Without A Cause , but this black-and-white production test is a chance to see the trio forging their chemistry.
Magic Moment: The silent end sequence sees the three actors goofing around, and Dean even gives Mineo a peck on the cheek.
The Test: Anybody who even considered auditioning for the controversial title of Lolita should have been halfway there, so it was just a matter of director Adrian Lyne checking Swain's potential in a filmed script reading with co-star Jeremy Irons.
Magic Moment: After ending a 'take, Swain coolly tells Irons he hit "the wrong cheek, by the way."
The Test: Aptly, Hannigan's try out for American Pie called for her to showcase her soon-to-be-famous band camp routine - and she got the part despite (or because of) stumbling over the key line.
Magic Moment: "One time, I stuck a f-f-flute up my pussy."
The Test: A great example of the kind of no-expense-spared demo Hollywood was used to in the Golden Age, this test for Hitchcock's Rebecca is lit so luxuriously it looks like the real thing, all the more so because of course Fontaine got the gig.
Magic Moment: Talking about a broken statue of Cupid, Fontaine asks, "Was it very valuable?" as if the thought of wealth has only just occurred, her eyes light up as she realises she's found a new way of dealing with her husband.
The Test: We see more of the African actor who played the title role in Alien here than in the film itself, as he gives a demo of how the xenomorph will move with a mocked-up head.
Magic Moment: The eerie stillness of Badejo's movements.
The Test: The nine-year-old Johansson tries out for the part in Jumanji that ultimately went to Kirsten Dunst.
Magic Moment: Talking about her "moron" school, Johansson already sounds like she smokes 40-a-day.
The Test: This might look like a joke, but Butler is auditioning for the title role in Dracula 2000 . Spoiler: he got the part.
Magic Moment: The camp ending, as Butler glides backwards and falls asleep into what we're guessing is an imaginary coffin.
The Test: Studios tested the troubled Marilyn to confirm she still had it before starting Something's Got To Give , the unfinished project from which she was fired just before her death.
Magic Moment: On this evidence - she still had it.
The Test: Casting Precious must have got easier once Sidibe turned up. Her naturalism is heightened further by awful picture quality that makes it look like she's just stepped onto a Jerry Springer-style reality show.
Magic Moment: After seeming huddled into her depression, Sidibe reacts like stung to a comment she doesn't like - "fuck you, you don't know nothing about my life!"
The Test: An epic 14-minute audition as Moretz goes through what feels like just about every major scene she has in Let Me In .
Magic Moment: "What's the matter? Are you scared of a little girl, huh?" Moretz asks with a sneer.
James Dean and Paul Newman
The Test: Friends and rivals Dean and Newman test together for East Of Eden . Only the former was cast, but Newman's chemistry shows why he became Hollywood's bright hope after Dean's death.
Magic Moment: The stars are asked to "look nose to nose." Dean keeps his intensity, but Newman can't stifle his laugh. That's the difference between their styles, right there.
Ellen Page and Olivia Thirlby
The Test: The Juno co-stars rehearse the lines that would make their names, hitting the rhythms of Diablo Cody's dialogue so naturally it's no wonder they got the parts.
Magic Moment: Page is outstanding throughout, but Thirlby trumps her with a delivery of a single word - "Gruesome!" - that captures the teenage mind's mix of shock and boredom.
The Test: Dietrich got her breakthrough part as saucy nightclub siren Lola-Lola in The Ble Angel on the strength of this test ( watch it on YouTube ), where her jokey singing gets serious when she loses her rag with the pianist. Even though it's in German, you get the effect.
Magic Moment: Over several takes, Dietrich gradually ramps up her aggression until she slams her hand on the piano.
The Test: Jackman's read-through with Bryan Singer for X-Men isn't as intense as a screentest proper (which might explain why, initially, he didn't get the part!) but it gives a flavour the actor finding the character he'd become synonymous with.
Magic Moment: Jackman forgets his next line! See, it happens even to major stars.
The Test: Christopher Reeve had already been cast as Superman when Channing was asked to play a scene with him. It'd not difficult to see why she didn't get the part - her Lois Lane would eat Clark Kent for breakfast.
Magic Moment: The ironic jazz hands as Channing checks out her reflection in the mirror.
The Test: This elaborate test with her The Parent Trap co-star Dennis Quaid could pass for the real thing, until Quaid breaks character and chats to the ten-and-a-half-year-old Lohan.
Magic Moment: Lohan rattles off a list of synonyms for Dad without missing a beat. In hindsight, the squandered potential is incredibly sad.
The Test: Russell Brand is given a breakdown of the scene for his Forgetting Sarah Marshall try-out, and proceeds to go down his own route.
Magic Moment: Brand surprises his co-star (and garners laughs from those in the room) by making horse noises.
The Test: Sam Raimi directed this Bruce Lee inspired showcase to convince studio execs of Tobey Maguire's action chops as Spider-man .
Magic Moment: The way-cool beckoning gesture that Maguire uses to start the fight is a classy Raimi-esque flourish.
The Test: Prior to her Oscar-winning breakthrough in Roman Holiday , Hepburn was interviewed on camera about her early wartime performances.
Magic Moment: "What did the Germans do about it?" the interviewer asks. Hepburn's face lights up: "they didn't know about it!"
The Test: This 1967 'personality test,' in which Hoffman's mix of confidence and reticence is palpable, must have been instrumental in helping the then-unknown actor to get his breakthrough role in The Graduate .
Magic Moment: Hoffman tells of winning a Best Actor award for an off-Broadway play, "which I felt was only forthcoming - it had to be." Then he adds: "since then, I've had nothing but bad luck," making his off-screen interviewer burst out laughing.
The Test: When the makers of Tootsie needed to check that Dustin Hoffman could convincingly drag up on screen, the actor parodied the whole concept of personality tests in 1981 by doing his mock-interview in character.
Magic Moment: Hoffman bullshits to the interviewer that he worked in England. What did he do there? "Royal Shakespeare."
The Test: Alfred Hitchcock was so certain that Tippi would be the perfect 'Hitchcock blonde' for The Birds that he greenlit an extensive $25,000 test, recreating scenes from earlier films with veteran character actor Martin Balsam, to persuade the studio.
Magic Moment: Balsam cheekily asks her what she thinks of Hitch "Does he treat you bad?" he goads. Hedren replies with mock-sauciness, "Terribly!"
The Test: These days, actors who want a role tend to send in homemade audition tapes. None works better than Stone's dry-run for Easy A , not least because the actual script requires a webcam confession.
Magic Moment: Halfway into her rat-a-tat monologue ("However, for those of you who are hoping that the sizzling details of my sordid past will give you reason to lock your door...") and Stone deftly flicks her eyes in the direction of an unseen door for a split-second without skipping a beat.
William Katt and Kurt Russell
The Test: Surfer dude William Katt tests for both Luke Skywalker and Han Solo in Star Wars , swapping roles with Kurt Russell. Katt is too knowing for Luke, but not knowing enough for Han... whereas Russell is very easy to imagine as Han Solo. Did John Carpenter ever see this footage?
Magic Moment: Russell's long, looks-could-kill pause when Luke tells Han they can't pay him.
The Test: Apparently, McAdams only got the script to audition for The Notebook the night before. It doesn't show.
Magic Moment: McAdams is so immersed in her performance she moves forward to yell, "Now I hate you!" catching the cameraman off-guard.
The Test: The hair's not right for Amelie , but Tautou's elfin daintiness, big saucer eyes and all-round childlike glee are there in spades, even without subtitles.
Magic Moment: The wordless sequence in which Audrey walks quizzically towards the camera and back again nails Jean-Pierre Jeunet's cartoonish sensibility.
The Test: Hardy got his break playing Picard's evil clone in Star Trek: Nemesis . His video screentest alongside Patrick Stewart highlights the edge he had even then - while Stewart is in Starfleet costume, Hardy is rocking a cool leather jacket.
Magic Moment: Hardy's voice is huskier in the screen test than the finished film. Combined with the jacket, there's a uncanny touch of Bane to his diction, albeit far easier to understand.
The Test: Had Roger Moore decided to call it a day as James Bond in the early 1980s, Josh Brolin's dad was first in line to replace him on the strength of this display of his action mettle.
Magic Moment: Brolin might flunk the closing wisecrack, but Moore never did a roll over a chaise longue after being punched.
The Test: Aged only 12, Portman confirms she's able to handle the tricky role of Mathilda in Leon .
Magic Moment: After being shocked and excited by Leon's way with a gun, Portman flirtatiously asks "And what did you say you did again?" with old-beyond-her-years maturity.
The Test: The English star nailed the tricky Southern accent as she beat just about every other actress in Hollywood in an infamously protracted casting process to find Scarlett O'Hara in Gone With The Wind .
Magic Moment: The chemistry with Hattie McDaniel, who would - like Leigh - win an Oscar for her role in the actual film.
Robert De Niro
The Test: The Godfather casting sessions threw up such riches that De Niro could test for Sonny and be second best. However, he got his reward from Coppola when the sequel was being cast.
Magic Moment: De Niro's ability to immerse himself in his character is obvious as he punctuates the line "You shoot em right up against their fucking head" by banging his fist against his own head.
The Test: Carell's Anchorman audition is arguably more like The Office 's Michael Scott than the Brick Tamland who ended up on screen, but he runs with a riff to the point where everyone in the room is ROFL-ing.
Magic Moment: Carell himself bursts into hysterical laughter and pretends to eat the "falafel hot dog" that's really a used coffee filter full of cigarette butts.
The Test: George Clooney puts Rockwell into character as Chuck Barris in a dry-run for Confessions Of A Dangerous Mind . The actor responds by improvising a mad, captivating solo dance routine.
Magic Moment: Rockwell does the splits. Wow.
Tom Selleck and Sean Young
The Test: Selleck came this close to playing Indiana Jones. On this evidence, he's too brusque for Indy - just as Sean Young would have been a tigress as Marion Ravenwood.
Magic Moment: Young gives Selleck a shove that looks realistic - until you clock that Selleck's turned his head to check where he's falling.
The Test: In 1947, stage sensation Brando was given pages from an unused screenplay for Rebel Without A Cause to show what he could do. He's electrifying - probably too much, since his Hollywood debut didn't come for another three years.
Magic Moment: Petulance turns to steel as Brando announces what he'll do to solve his problems. "I'll get a gun," he says, a half-smile, half-sneer flitting across his face.
The Test: The future Harry Potter , aged 11, gives a life-changing rehearsal for the schoolboy wizard. He's not quite Harry... and then the glasses come on and the casting is sealed.
Magic Moment: The delighted reaction to birth of Norwegian ridgeback - not bad going for an actor who would spend the next decade reacting to green-screen.
Daniel Radcliffe, Emma Watson and Rupert Grint
The Test: During the same casting session (scroll to 8:00 on the video), Radcliffe confirms his chemistry with his soon-to-be co-stars… although the producers lose marks for giving them the American Sorcerer's Stone script.
Magic Moment: Rupert Grint has already nailed Ron's expression. He hardly has a line, but he doesn't need any more.
Robert Downey Jr
The Test: Even in a glossily professional studio test, with the actor's biggest gig at stake, Downey Jr nails Tony Stark with such insouciance it looks like he's not even trying.
Magic Moment: A take starts, and Downey Jr is making the other actors laugh - is this part of the scene? No idea, but the charmer soon segues effortlessly into business.
The Test: Stone nervelessly essays what was to be her signature role, Catherine Tramell in Basic Instinct , alongside Paul Verhoeven - probably the only director who could withstand her piercing, lustful stare.
Magic Moment: "You know I don't like to wear underwear," she says, dropping a voice to a conspiratorial whisper to add, "Don't you, Nick?"
The Test: Ford reckons he was cast as Han Solo because George Lucas got used to him being around. But it's clear from the footage that the actor's world-weariness was made for the character.
Magic Moment: Look at other Han Solo screentests and they do the line as written: "I'm a freebooter, not a revolutionary." Ford adds an icy, disparaging "boy" halfway through the sentence.
The Test: The young star, testing with Harrison Ford, essays the boyish enthusiasm that separated him from other hopefuls for the role of Luke Skywalker. He's so carried away he calls his co-star Hans instead of Han.
Magic Moment: Luke gets passionate telling Han (in a scene rewritten before filming began): "I doubt if the actual security there is much greater than on Appalyer-Sullust and what there is is most likely directed towards a large scale assault." Famously, Hamill later mocked the line by asking, "who talks like that?!"
The Test: One of the most stylish tests around, as Weaver arrives fully-formed as Ripley, in costume and with a cigarette wrapped to her lips while Ridley Scott tracks the camera around a mock-up of the Nostromo set.
Magic Moment: Weaver's wry near-smile after she Parker a ticking off over the comlink.
The Test: Carrey really, really wanted the role of Andy Kaufman in Man On the Moon . Hence this epic audition piece, in which Carrey improvs a variety of Kaufman-esque routines.
Magic Moment: The bongo playing.
The Test: Francis Ford Coppola went to extraordinary lengths to ensure that Pacino won the role of Michael Corleone in The Godfather , from pairing him with eventual co-star (and real-life friend) Diane Keaton, to convincing James Caan (who more or less had Sonny in the bag) to do a deliberately muted read-through.
Magic Moment: Pacino's command is obvious. As editor (and George's wife!) Marcia Lucas told Coppola, he had to cast Pacino because "he addresses you with his eyes."
The Test: The famous audition where Thomas conjured up his feelings for his dog to convince Steven Spielberg he had the emotional range to play Elliott in E.T.
Magic Moment: The tears roll. "You can't take him away, he's mine." Heartbreaking.