Shrek isn't like most film stars. He doesn't get paid a lot of money. He doesn't look good. In fact, he's big, green, ugly and bad-tempered. But the biggest difference is that Shrek only exists in the computers of the Dreamworks film studio. All of the characters in the film Shrek were created using a technique called 'computer-generated imaging', or CGI.
Shrek was not the first film to be made using only CGI technology. That was Toy Story, in 1995. Butit was the first time film-makers had tried to create realistic human characters. One of these characters was Princess Fiona. To make her move as realistically as possible, the film-makers first created her skeleton on the computer. They added muscles and told the computer how the muscles should work. Then they added her skin. But she still needed one thing-a voice.
The character's voice is probably the only thing that can't be created with a computer. For that, you need a real actor. To do the voice of Princess Fiona, the film-makers got Cameron Diaz. For Shrek they got Mike Myers, the star of the Austin Powers films. Neither actor had done an animated film before. 'It was fun because you don't have to worry about your hair and make-up the lights, or where the camera is,' says Diaz. 'You just go out there and play.