In every film there are many opportunities for 'moments', short but hugely satisfying seconds when everything seems as if creativity has not only a sense of humour but also no limits. Often these are mistakes, left in for their serendipitous nature. Some moments are unexpected, some work because they are oh so predictable. Some fall out of the sky and others sneak up on you. All have one thing in common; they delight whether in the middle of a tense action sequence, a horror effect, a love scene or a knockabout farce. Their DNA is human but their effect divine. I'm not talking about pay offs to long signposted plot threads (Shyamalan's glasses of water in Signs is a good example of this). I'm talking about the after thoughts, the on set "What if we did this..." moments, the unplanned accidents, the metaphorical water droplets that slink cheerfully through tight armour-plated plot. When Andrew Robinson, chained gorily to hooks that pierce almost every last square inch of his flesh at the dénouement of Hellraiser, he didn't say what Clive barker had written (I believe that was "Fuck you!"). No, he improvised the line, the shortest verse from the bible, "Jesus wept..." Perfect. That is what I mean by a moment.

A movie by definition (almost) is planned, directed and assiduously controlled. There are great moments in animation to be sure but none that have been accidental for obvious reasons. The ultimate metaphor or indeed condition of that tightest of control is CG effects. The film-maker, by proxy of skilled digital artists and technicians, has control of every pixel of the screen. Accidents don't happen in this milieu and if they do, it takes a brave filmmaker to present them to an audience. There was a flaw in the render of a Gollum CG scene that resulted in his hair sticking up vertically throughout the action. I didn't make this up. It's in the Extras of Lord of the Rings: The Two Towers. When that control is relaxed sometimes miracles happen. Let's not get too messianic here. I'm talking about those moments that you subconsciously recognise as mistakes but accept them and subsequently fold them into the fabric of the drama. They make you feel not so much as if you've just witnessed your child's first steps, but provide a gentle nudge that makes you gleeful nonetheless. It's that rather effeminate squeal of delight possibly accompanied by a jiggle of shoulders and 'Wallace' closed hands. If you're not that effusive, it is definitely accompanied by the smile that recognises the right choice has been made. The film-makers choose those moments from thousands of others and as Slarek may well agree [I most definitely do – Slarek], a movie without a mistake or mis-step feels as if it may have come off an assembly line or something put together by the bottom line and not a single free, independent, creative mind.

Before diving in to some examples, let me state my favourite 'mistake' to serve as permission for all the others. Even the great Stanley Kubrick knew the food would slip back down the straw in a scene from 2001 (set supposedly in Zero G). But Stanley was shooting in England, a place not renowned for its lack of gravitational pull. Did he tear his hair out for a solution (even I could come up with a solution to that little dilly of a problem)? No. He left it in. If Kubrick can pass an all too soulful reminder of the human element in the film-making process, then so can we all. Be clear that I'm not talking about simple mistakes such as the hapless Stormtrooper who smacks his head on a door frame on the Death Star in the original Star Wars. I'm talking about those moments that tell us things about character or story seemingly made up on the spot; things that seem so extemporaneous, it makes your heart soar.

One of the most famous happy accidents happens in the very first shot of a sixties movie directed by the then irrepressible Richard Lester. The most famous four people in the world are running away from their fans. I'm sure Lester took a very loose stand directorially in his A Hard Day's Night. The Beatles weren't actors but had very specific characters nonetheless. The least defined or 'known' of the fab four, George Harrison, takes a painful tumble on a stone pavement in a move (and I chose my words carefully) that would be simply impossible to perform regardless of the skill of the actor. A trip and stumble like that has to be real and this little piece of business almost defined what was to follow – happy accidents. Yes, there was a script but you come away with the impression that each of the four was simply being themselves (hard for actors, that talent) while Wilfred Brambell and John Junkin did their best to propel a silly plot along. George's tumble (and yes, it really looks painful because it was real) succeeds in setting up the 'je ne sais quoi' of an entire movie. No mean feat.

One of the classiest bits of business I've seen in the many years I've been paying to be left in the dark concerns an act that would have prompted me to express undying devotion to the performer concerned (if it was her idea). I will give the writers credit here because it certainly feels like it was an organic part of the sequence but because of its nature, I'm giving it 'moment' status. Idly thinking of who might have come up with the moment explains a lot if Joss Whedon's rewrites and polishes of this particular movie's screenplay are to be accepted. Here's the sitch (as JW may say). You're driving a bus that cannot go below 50mph or it will explode. It is being tailed by lots of police cars. At your elbow is an attractive FBI man who looks like, for all the world, that Neo fellah from The Matrix. You've all been told that up ahead is a right turn that the Stig would balk at but the driver has no choice. Everyone could die. Everyone's fate is in her... feet. Her hands are simply steering. Yes, it's the movie that bestowed fame upon Sandra Bullock, Speed, directed by a Dutchman who seems to have disappeared off Hollywood's radar like HD-DVD stock, Jan de Bont. Imminent death... Death defying action required. She's about to make the right turn of her life... What does she do? She indicates. Oh my. She indicates. Here is a bus, on its own as a bus, accompanied by scores of concerned vehicles. Everyone, with the exception of the panhandler on 31st street, knows the situation and Sandra Bullock indicates to let everyone know – who already know – that she's about to turn right. It's the sort of moment that makes men like myself lose their common sense.

Let's have a scene in a movie that shows the two leads they weren't crazy after all. We're three quarters of the way through the film and both leads have been implanted with an image (an image I hope to visit on my Wyoming trip this year). She paints it, he sculpts it. Eventually after meeting up, they set off cross country and in a rather self important "Oh, this is significant!" scene – an attribute which we'll forgive because I adored the film – they see the image that's been taunting them... Sticking out from the flatlands of western America is Devil's Tower, the iconic terrestrial image from Spielberg's Close Encounters of the Third Kind. Melinda Dillon and Richard Dreyfuss stop the car and slowly climb the bank where a sweeping camera move and John Williams' soaring symphonic orchestra say "You're not crazy!" The grandeur and awe of the whole mise-en-scene is very subtly undermined by the fact that Melinda Dillon slips as she's walking up the dusty slope. There must have been other takes but Spielberg chose the one with the most humanity. Bravo.

As this article could conceivably never end (moments come to me as I type) I will simply list ten of my favourites and invite you to think of those that mean something to you. In absolutely no order whatsoever save the firing neuron order in my brain, here are ten small treats that may have passed you by...

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Robin Hood Prince Of Thieves
Yes, yes. Forget the Americanised Robin Hood and the absurdist apologistas on offer regarding the crusades and dark skinned Moors. Yes, Rickman's Sheriff of Nottingham stole the show but it's also a Rickman scene that prompts this singular moment. In something of a hurry to consummate his hastily arranged marriage to Maid Marion, Rickman has to (let's not be coy) rape Elizabeth Mastrantonio. We know Robin will rescue her but the lead up features a shot from the ground at Marion's feet as Nottingham prises her legs open. I think this is supposed to be a comic moment (it's not despite the voluminous underwear on display) but what follows is sublime. Nottingham's witch, played by a barely recognisable Geraldine McKewan, places a small pillow beneath Mastrantonio's head. The gesture is enough but Rickman's exasperation at such thoughtfulness is the icing on this moment's cake.

It Happened One Night
Frank Capra's wonderful knockabout romantic comedy still stands up all these years. Don't be vintage-averse – check it out. Clark Gable is accompanying a spoiled brat heiress (Claudette Colbert) across the country so she can meet up with and marry her beau. Gable is the wiseass reporter, who of course, succumbs to her charms. Halfway through the film, Gable has to scare someone away and after successfully convincing the sap that he's part of the mob, he sees the guy off with a jaunty spit that would have been the cool full stop at the end of the scene. The ejected saliva lands on his shoulder. He's just an average schmuck and we love him for it.

Roxanne
Steve Martin's take on Cyrano De Bergerac is chock-a-block full of wonderful touches, most of them scripted no doubt. But in the final argument between Martin and Daryl Hannah, she opens the door of her house and throws his hat at him. Martin manages to catch in about four goes, each one knocking the hat up into the air until he finally brings it under control. That's not in the script but it's pure Martin.

Local Hero
Burt Lancaster wants to build an oil refinery on a charming Scottish fishing village and the villagers are thrilled (money, of course). Stopping the deal is Ben, the local beachcomber who actually owns a significant part of the beach. It's up to Mac (Peter Riegert) and Fulton Mackay to do a deal, mano a mano. Mackay picks up a handful of sand and asks "Would you pay me a pound for every grain of sand I have in my hand?" Then, some sand falls away and like the old pro he was, he seems to improvise a line (I simply cannot imagine this was in Bill Forsyth's wonderful script though you never know). "Saved you a few pounds there..." Magic.

Road Games
I've already mentioned this in my DVD review so I'll be brief. No actor on planet earth could have done what Stacy Keach did with a motorcycle trying to go after a suspect. Forget script, forget planning. That machine took Keach for a ride in the most marvellous way. It's close as a moment to actually taking you out of the movie because the moment is so perfectly real.

Brazil
Gilliam's Orwellian fantasy – still strong after all these years – has a small moment in it that delights me every time I see it. Sam Lowry (Jonathan Pryce) meets his mother (Katherine Hellmond) at a swanky drinks do. She's trying to introduce him for the second time to a prospective girlfriend, Shirley (Kathryn Pogson). They sit together, awkward in each other's company and Pryce tries to defuse the situation. Pogson, her mouth held in a wraparound brace, finally summons up some honesty and to Pryce's surprise, she says "I don't like you either." Enter Michael Palin and Pryce gets up standing on Pogson's toe as he does so. Watch Pogson's face – again, no way could this be scripted. It goes from regrettable honesty to a little sympathy, cut off by acute pain and catching Pryce's eye, her face instantly snaps back into "Think nothing of it!" territory and when Pryce has moved off, glowering anger and resentment settle. All this in about three seconds. It's a piece of acting I've never forgotten. Wonderful.

Defiance
Mentioned on the commentary by the director so I know this moment was 100% serendipity... It's World War II, occupied Poland. Liev Schreiber has just been told his wife is dead and Daniel Craig goes to comfort him. Schreiber smashes his head against a tree pre-rigged with blood and to the director's dismay, on what was developing into the best take, the blood did not appear... until at the climax of the emotion, a small drop appeared running from underneath Schreiber's hair. You cannot plan these things, things that the best directors take advantage of – as did Edward Zwick.

Doctor Who
Not a movie moment but a TV moment worthy of praise. People who go that extra mile are generally regarded very positively in the film and TV business. The Mill is an FX company that has done some amazing work and as Russell T. Davies said when they don't turn in amazing work, it's because the producers haven't given them the resources to do so. But in one Tardis dematerialisation (I believe the episode is The Unquiet Dead from Eccleston's era) there are snow flakes which fall and disperse from the Tardis' ridges and they spiral away in a tiny piece of detail that some wonderful digital FX person has chosen to add. That's going the extra mile.

The Exorcist
Not strictly a moment but because I know so much about this movie, it stands as one because of the veracity and truth of the performance on offer. The actor playing father Dwyer is no actor. He is in fact a real man of God (Reverend William O'Malley S.J) who's still active. Director Friedkin saw something in him and he does a great job at being father Karras' best friend. But he's no actor so in the more demanding scenes – or one in particular – Friedkin had to give him some, uh... inspiration. Look at the touching final scene between the two friends. O'Malley acts like he was born to it, his voice and hand trembling as he performs the last rites. There's a good reason for this thespianic excellence. Seconds before the take, Friedkin asked O'Malley if he trusted him. "Yes," said O'Malley and Friedkin smacked him hard across the face... "Action!" Look at the scene. You can almost see the welt on his face. Priceless. Not sure anyone would get away with that today.

Legend
Again, practically unscripted but you must always doubt that anything can happen on a Ridley Scott set without the maestro having included any potential outcomes in his multi-layer confection of a movie. Mia Sara is a fairy tale princess, Lili, being wooed by a young Tom Cruise, Jack. The movie did not light up the box office despite the astounding creation of 'Darkness' as performed by Tim Curry (artist) and aided by the stunning work of Rob Bottin (make up artist). This is a very simple moment but a magical one nonetheless. The princess is being courted and her coy behaviour is driving Jack nuts, as it should. At one point near some greenery, she stops and turns. One coil of her curly hair has looped around a thin branch and as she turns it unravels, slips off the branch and re-coils. It's a beautiful moment that I'm sure Scott made up on the spot.

Postscript
As we travel further into the digital realm, there are fewer and fewer moments because of the nature of the 'ambition of perfection'. Here's a plaintive cry to keep idiosyncrasy and human fallibility as part of the movie creative process. Perfect is merely perfect. Imperfect is much more interesting...