“Believe me, if we could have done it the traditional Aardman way, we would have.” Sam Fell, the co-director of Flushed Away, is explaining why Aardman Animation, the maestros of Plasticine and stop-motion animation who brought us Chicken Run and the Wallace and Gromit movies, have made their first computer-animated feature with the Shrek studio DreamWorks. “The scale of the story, not to mention all the water involved, made CG the only option,” he says.

From an idea about pirates and rodents, Flushed Away ended up more like “The African Queen with rats in a sewer”. A pampered but lonely pet rat (voiced by Hugh Jackman) living in a Kensington flat is flushed down the toilet into a parallel sewer London of double-decker buses, shops, pubs and boats made out of household items and populated by rats, singing slugs and a villainous toad (a fruity Ian McKellen) who wants the sewers to himself.

Although the film, a mix of droll humour and busy chases, was made at DreamWorks in Los Angeles, the characters still look like their lumpen, monobrow Aardman predecessors back home in Bristol. “We didn’t want the film to look too slick, that’s part of Aardman’s charm,” Fell says. He and his fellow Brit director David Bowers had to get the American animators to unlearn their natural instinct to make everything shiny and bright. “Perhaps it’s the LA sunshine, but American cartoons have this brighter, sleeker look that can tend to look the same.”

That’s a bit of an understatement. Looking back on what has been the busiest year for computer-generated animation, can you distinguish the zoo animals lost in the jungle in The Wild from those in Madagascar? Or the story of the chicken with a disapproving father in Chicken Little from the cow with a disapproving dad in Barnyard? Or the images of urban sprawl and villainous exterminators in The Ant Bully and Over the Hedge? And what about all those selfish characters, whether animal (the pampered bear released into the wild in Open Season) or mechanical (the arrogant racing car in Cars), learning the value of teamwork and thoughtfulness?

“The similarity of some cartoons this year is undeniable,” says the director George Miller, whose eclectic career includes Mad Max, everyone’s favourite talking pig Babe, and now the Warner Bros cartoon Happy Feet. He admits that when his animators began work on the film, they tended to do low-rent imitations of hits from DreamWorks and Pixar, the CG brand leader behind Toy Story, Finding Nemo and The Incredibles.

“Then we found that the technology just got better and better as we worked on the film,” Miller says. “When we began pushing the animators, they produced some amazing stuff. I think our decision to go for a photo-realist look turned out to be a plus for us.”

So expect the tale of an Emperor penguin (Elijah Wood), who is unable to sing and so attract a mate but can tap-dance, to hoof its way through an Antarctica worthy of National Geographic, complete with exhilarating underwater penguin ballet.

Flushed Away and Happy Feet find themselves in an overcrowded Toontown. “This year has seen the result of the gold-rush mentality that prompted many animation start-ups trying to get a slice of the DreamWorks and Pixar pie,” says Rick DeMott, the managing editor of the online trade magazine Animation World Magazine. “We have ended up in a kind of cracked, pop culture-saturated wonderland.”

Next year we get more penguins with Sony Pictures’ Surf’s Up, a mockumentary about surfing penguins. And more rodents with Pixar’s Ratatouille, in which a rat with a taste for the finer things in life discovers his destiny in, yes, a sewer.

Such lookalike stories weren’t a problem when Disney was the only game in town but that has all changed. “The technology means that it no longer takes a major studio to make a feature- length animation,” DeMott says. “Often, studios prefer to bankroll a production rather than set up their own animation division.”

Happy Feet is among several cartoons, including Barnyard, The Wild and The Ant Bully, made by independent outfits with studio money. It took Miller’s company more than two years to transform the Australian special-effects house Animal Logic into an animation studio before work began on Happy Feet.

Pixar developed in much the same way, building on a foundation of homegrown technology and visual effects as a tiny spin-off of Lucasfilm, George Lucas’s company. It became such a powerful player that this year it was bought by Disney for $7.4 billion (£3.9 billion).

“I can’t tell you how many people have come in and said, ‘We’re going to build the next Pixar’,” Julia Pistor, the vice-president of Nickelodeon Movies, told the Hollywood trade daily Variety. “But I think there is a glut of activity when what we are looking for is the talent and the story.”

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