LONDON, England (CNN) -- This month on the Screening Room we're turning to the wonderful world of animated films.

"Shrek the Third," the latest in Dreamworks' inverted-fairytale franchise

Blockbusters like "Finding Nemo" and Dreamworks' franchise "Shrek" have turned animation into a multi-billion-dollar industry, and a market once dominated by Disney is becoming crowded with competition.

This year, Pixar celebrates its 20th anniversary. From "Toy Story" to "Ratatouille," the company has transformed expectations about what's possible with animated film.

Pixar's position as a world leader in animated film is largely down to John Lasseter - considered by some to be the Walt Disney for a new generation. From "Toy Story" and "A Bug's Life" to "Monsters, Inc." and "Cars," the Pixar back-catalogue is a testament to his creative genius. And when Pixar merged with Disney he became one of the most powerful players in the movie business.

The first Pixar production released since the merger is "Ratatouille," the story of an unlikely alliance between a blundering trainee chef and a gourmet-loving rat.

"Ratatouille" director Brad Bird's credits for Pixar include the Oscar-winning feature "The Incredibles," which won critical plaudits for its ground-breaking animation.

He told CNN, "I think that one of the nice things about Pixar is that they don't feel like they have discovered the secret formula to making a good movie. They just keep focused on trying to make a movie that they would want to see. We are challenged and surprised every time they work out."

But while Pixar and Disney may be the giants of animation they face formidable competition from another box-office monster -- Shrek.

The adventures of the world's favorite ogre have generated a total of two billion dollars in takings.

Actor Mike Myers, who voices Shrek, told CNN that he thinks the movies' appeal is their unlikely hero. He said, "With 'Shrek,' they took fairytales and turned them on their heads. Everything is inverted. Traditional villains are heroes, traditional heroes are villains. The whole team decided, we're going to look at somebody who has been told he was a villain and we're going to make him a hero. That's when I knew they were on to something."

The success of the Shrek franchise, supported by other big budget features such as "Madagascar," has cemented Dreamworks' position as a major force in the animated world.

Another successful franchise -- "Ice Age" -- has been a hot seller for 20th Century Fox.

And the polar climate has also been kind to Warner Brothers with last year's Oscar-winning "Happy Feet" charming audiences around the world with a tale of dancing penguins, while the Tom Hanks-voiced "The Polar Express" also scored well on its way to becoming a seasonal stocking-filler on DVD.

The life-like motion-capture technique used in "The Polar Express" will also feature in Warner's forthcoming release, "Beowulf" featuring Angelina Jolie.

But in a market dominated by 3-D CGI animations, one of the big three summer blockbusters this year belongs to a more traditional form of the art.

"The Simpsons Movie" is the world's longest-running animated television series, and fans have eagerly awaited its move to the big screen. Creator Matt Groening told the Screening Room, "We've had fans clamoring for a movie for the past 18 years. We've had kids, they've grown up, they've become adults, they've become writers for the Simpsons, so we had to do a movie after all this time."

So, will Springfield's most famous inhabitants break all former animation records? Groening and co. will certainly be hoping that the movie gets a box-office "Woo hoo!" from its fans.

"Happy Feet" is a Warner Bros. film; Warner Bros., like CNN, is a unit of Time Warner. E
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