Darth Vader (Star Wars)
Impact: Be honest, if there anybody under the age of 40 who hasn't tried to imitate Vader's respirator rasp?
For once, here was a movie where it was the villain, rather than wet hero Luke Skywalker, who became the one to copy.
Influence: Vader raised the stakes for sci-fi bad-asses, both in the visceral presence of that fetish-gear shock troop clobber and George Lucas' unprecedented decision to have the whole story revolve around him.
It's possibly this confusion that led Dick Cheney to admit he was the Darth Vader of American politics, and actually be proud of the fact.
If He Hadn't Existed: Dave Prowse would still have the Green Cross Code man royalties.
Jeff Spiccoli (Fast Times At Ridgemont High)
Impact: Fast Times At Ridgemont High wore its research (by future director Cameron Crowe) on its sleeve, ensuring the most realistic portrayal of high school life to date.
Nowhere more so than in Sean Penn's joyously bodacious surf dude, Jeff, for whom even school is bearable once the pizza is ordered in.
Influence: Penn's winning portrayal predated the uber-cool Ferris Bueller by four years, but it wasn't until the turn of the 90s that it became clear that Spiccoli had invented the screen slacker ahead of Bill and Ted, Wayne and Garth, and the collected characters of Richard Linklater.
Spiccoli's influence on Sean Penn, however, appears to have been less than zero.
If He Hadn't Existed: Watching school on screen would be a lot closer to actually being there.
The Gunslinger (Westworld)
Impact: Yul Brynner's steely presence as the android cowboy, remorselessly hunting down tourists in a buggered-up sci-fi theme park, was especially unnverving because the actor showed zero sign of emotion.
Influence: The cyborg quickly became a mainstay of sci-fi cinema, offering potential for shock reveals ( Alien ), pathos ( Blade Runner ) and the tech-noir horror of the Terminator.
Arguably, the Gunslinger's sheer otherworldliness also fed the growing trend for predator cinema in Jaws , Alien and - well - Predator . One thing we do know, given Michael Crichton's involvement in both Westworld and Jurassic Park , is that Yul Brynner is the T-Rex.
If He'd Never Existed: The bad guys would still insist on nattering away about world domination, instead of getting on with the kill-shot.
Gollum (The Lord Of The Rings: The Two Towers)
Impact: In George Lucas' imagination, it should be Jar Jar Binks on this list. But that all-CG creation's impact proved a negative one, earning fanboy scorn and showing up the difficulties inherent in mixing live action celluloid with animated characters.
Peter Jackson, aided by WETA's FX bods, went one better by filming the actor - Andy Serkis - in character (albeit dressed in a big mo-cap suit covered in balls) and using his movements and nuances to make Gollum an integral part of the on-screen action.
Influence: Mo-cap is now the industry standard means of creating CG characters at the top end of Hollywood, with Robert Zemeckis making it second nature.
James Cameron refined the technology to new depths of visual subtlety in Avatar, but it's Serkis and Jackson who remain the go-to guy for breathing life into characters, with their King Kong improving upon Gollum.
If He'd Never Existed: The Jar Jar backlash would probably have led to Hollywood using hand puppets.
Alex Forrest (Fatal Attraction)
Impact: Dan Gallagher's (Michael Douglas) affair with Glenn Close's damaged lover sent shockwaves through middle-class America for showing the dangerous effects of adultery.
Chiefly, though, it was Alex's increasing madness, culminating in her boiling Dan's daughter's bunny in a pan, that initiated the most debate. A decent female villain, or a misogynistic portrait of a loon?
Influence: Fatal Attraction's "yuppies in peril" structure led to a cycle of variations on its suburban stranger danger thrills, notably Pacific Heights and The Hand That Rocks The Cradle .
But Glenn Close's immersive performance kickstarted a Golden Age for powerful female roles, not only for her ( Dangerous Liaisons ) but also for the likes of Angelica Huston, Michelle Pfeiffer and Thelma and Louise themselves, Geena Davis and Susan Sarandon.
If She'd Never Existed: We wouldn't know what a 'bunny boiler' was.
Catherine (Jules Et Jim)
Impact: The French New Wave was still in its infancy when Jeanne Moreau's freewheeling Catherine seduced Jules et Jim in Francois Truffaut's off-the-cuff masterpiece.
Her beguiling presence - temptress, best mate and worst enemy rolled into one - sealed the sense that here was a provocative, thrilling and very sexy new way of making movies.
Influence: Catherine ushered in a new type of screen sexuality from Brigitte Bardot's more brazen flesh, and helped to define 1960s permissiveness (or, to put it another way, freedom) for fellow French actresses like Catherine Deneuve and also for English speakers like Julie Christie and Jane Fonda.
If She'd Never Existed: The Carry On films would be seen as a high water mark in cinematic sophistication.
Harry Potter (Happy Potter & The Philosopher's Stone)
Impact: Potter was always going to be huge, but that didn't necessarily mean the films would be any good.
Warner Brothers' commitment to keeping the essence of J.K. Rowling's stories intact is confirmed by allowing Daniel Radcliffe to grow in tandem with the role, from gauche novice Hogwartian to full-blooded wizarding warrior.
Influence: The family fantasy genre has remained in thrall to Rowling's vision for the past decade, with Eragon , The Golden Compass , The Chronicles of Narnia and Percy Jackson and the Lightning Thief all coasting on Potter's success.
But the character's influence arguably goes wider. In an age when audiences are accustomed to the long haul of DVD box sets, the scope and scale of Potter/Radcliffe's emotional journey has changed the rules about screen acting and star power.
If He'd Never Existed: Child actors would continue to go totally off the rails as soon as they hit their teens.
Impact: Toshiro Mifune had wowed global audiences as the human hurricane in Kurosawa's Rashomon and Seven Samurai .
Yet it was as Sanjuro - aka Yojimbo , the bodyguard - that Mifune distilled his screen presence into a cackling, apparently amoral soldier-for-hire who played off rival factions in a vicious gang war to save the town...and earn a bit of money into the bargain.
Influence: Most obviously, Mifune's chin-scratching, perpetually amused warrior was the direct inspiration for Clint's Man With No Name, creating the post-modern action hero who would rule the roost in '80s and '90s action movies.
In the East, too, Sanjuro cast a formidable shadow, inspiring blind swordsman Zatoichi and, later, the killers-with-conscience of John Woo's blast-em-ups.
If He'd Never Existed: Action heroes would never have got so naughty.
Susan Vance (Bringing Up Baby)
Impact: Surprisingly little on '30s moviegoers. Bringing Up Baby flopped, perhaps because of the rumour that Katharine Hepburn was box-office poision.
But Susan - the upper class kook simultaneously ruining Cary Grant's life by releasing his inhibitions - caught on with a later generation that valued the screwball wit of Howard Hawks' film.
Influence: From the late '60s onwards, Susan became the inspiration for rom-com heroines everywhere, from Barbara Streisand in What's Up Doc? , to Diane Keaton in all of her collaborations with Woody Allen.
To vastly diminishing returns, the likes of Kate Hudson and J. Lo have also been trying to replicate Hepburn's nonchalant chaos.
If She'd Never Existed: Rom-coms would be 'boy meets girl,' instead of 'girl drags boy on mad adventures involving a leopard.'
Impact: Bram Stoker's famous vampire slunk onto screens as Nosferatu 's weird (and copyright-bothering) deformity Count Orlof, but it was Hollywood's official adap - starring Bela Lugosi - that popularised Dracula as Transylvania's most cordial, diabolically polite blood-sucker.
Influence: The vast majority of screen Draculas follow the 1931 template (most famously, Christopher Lee's British gent version). But the wider influence of Lugosi's interpretation is to forever seal Hollywood's villains as suave, otherwordly and - crucially - foreign.
If He'd Never Existed: The scariest thing that Hollywood villains would want to drink would be a bottle of Chablis.