Mickey Mouse has featured in films, TV shows, video games and merchandise
If you go back to the origins of Mickey Mouse and look at the characters that appeared in those early films, there were all kinds of farmyard animals - pigs, cats, dogs, goats, horses, cows and mice, and they were all a realistic size.
As the characters became more rounded and more sophisticated over the years, their animal nature regressed and they became more like people.
Mickey is a character who wears shoes, shorts and strange white gloves, he lives in a house, drives in a car and has a pet dog called Pluto. In itself, it is rather strange that a mouse has a dog as a pet.
Even if it's a small dog, it still means Mickey is enormous for a mouse.
MICKEY THE SYMBOL
Over the years Mickey Mouse has been a symbol of different things at different times.
In the 1930s, the time of the great depression, Mickey represented something very American to do with endurance and the ability to rise above defeat.
Micky Mouse video clips - courtesy Walt Disney Home Entertainment
Alongside Charlie Chaplin, he was an icon of the little man. They symbolised hope, optimism and a kind of inbred spunkiness.
In the first film, Steamboat Willie, he is rude to the authority figure, blows raspberries, thumbs his nose and is generally a little scamp.
As life improved in the 1940s, Mickey became redundant.
Disney had become the doyen of family entertainment and Mickey could no longer be the impertinent, revolutionary character.
So as Disney became more respectable, so did Mickey.
He became the MC, the compere or the circus ringmaster for a whole galaxy of characters like the irascible Donald Duck and the inept Goofy.
He became the pole of normality around which this bizarre entourage flew like satellites.
Move into the 1950s and Walt Disney started opening the first of his theme parks.
Mickey took on another role as the genial, mute host, the friendly person in a suit, welcoming people to this fantasy wonderland.
Now, in 2008, children are watching Mickey's Clubhouse on TV with a digital Mickey Mouse, and he is rejuvenated again.
MICKEY AND WALT
Mickey Mouse was incredibly important to Walt Disney.
In 1928 he had lost the rights to the character he was then animating - Oswald the Lucky Rabbit - a character not entirely dissimilar to Mickey but with floppy ears instead of round ones.
Disney's New York distributer decided to snaffle the rights to the long forgotten rabbit and sign up most of Disney's artists at the same time.
According to Disney legend, on the train back from New York, Walt Disney came up with the idea of an animated mouse.
He wanted to call the mouse Mortimer, but his wife Lillian convinced him that it was the worst possible name for a cartoon star and he agreed to change it to Mickey, apparently because he had Irish blood.
On returning to California he started working on the first Mickey films - Plane Crazy and Galloping Gaucho, with his collaborator Ub Iwerks.
But before they were released, the movie industry was revolutionised by the arrival of the talkies.
It is a sign of Walt Disney's entrepreneurial acumen that at a time when people were doubting the efficacy of this strange new medium, he seized on the opportunity, shelved the first two films and made the third film, Steamboat Willie, in glorious, cacophonous sound.
It was the first ever cartoon with synchronised sound and was a huge success. It established Disney and kick started Hollywood animation in a new direction.
MICKEY THE CIRCLE
People used to say Mickey Mouse was very simple to draw, that any animator could draw him.
Mickey Mouse was Walt Disney's favourite character
You simply drew the head by drawing around a dollar, then drew the ears by drawing around a quarter.
That is the secret of Mickey Mouse - he is based on circles.
We respond to round characters far better than to spiky, sharp characters.
What they created, whether knowingly or not, was a character that had qualities of safeness, femininity and security.
A psychologist in the 1940s even said that if you showed a picture of Mickey Mouse to a child in a crib, that child would instantly smile.
The truth of the matter is that Donald Duck is much more entertaining, but what we have in Mickey is something very secure.
The shape is what endures. It is why Mickey was so obviously designed (although nobody knew it at the time) to be turned into cuddly toys and all sorts of other merchandise.
Go into a Disney store and it is full of exercise books and children's toys and children's clothing. People want to have a bit of Mickey.
MICKEY THE ICON
Andy Warhol said that Mickey was one of his favourite images. Even the Palestinian militant group Hamas used a Mickey-like image on their children's TV programme, spreading the message of Islamic Jihad.
It is fascinating that a character who hasn't made many movies in the last 20 years still has worldwide fame.
Maybe it is the fact that Walt Disney himself invested so much interest in the character.
He would often say to the animators in his studio, working on full length, big-budget films: "I hope you will never forget that this was all started by a mouse."
American philosopher Ralph Waldo Emerson was supposed to have said that if you build a better mouse trap the world will beat a path to your door. Disney just made a better mouse.
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