They're big budget, big grossing films, featuring big name stars doing the voices. Cartoon films are not child's play for Hollywood's A-listers.
"Mike Myers got paid how much?"
It's a not-truism of cartoon movie magic. Donkey, loyal sidekick of Shrek, looks down his long nose in disdain at Puss-in-Boots, comic foil and feline annoyance.
"I'm sorry," Donkey shouts at Puss. "The position of annoying talking animal is already filled."
Not so when it's Eddie Murphy and Antonio Banderas doing the talking, their spats moderated by Mike Myers' ogre. What animated Hollywood features such as Shrek 2 prove is that there's always room for another celebrity.
Shrek 2 has already grossed more than $400m since its release in the United States, and it looks set to do brisk business now it's opened in the UK to cinemas full of children - and adults - many sporting green ears in homage to their favourite ogre.
For the kids, it may not matter that Banderas is spoofing his macho character in The Mask of Zorro. For the adults who pay for the tickets - and the actors on the cast list - it counts.
"The quality (of animated features) has improved so much that the actors are more readily available - and they also get good deals," says Stuart Kemp, the UK bureau chief for the Hollywood Reporter.
Big names, big profits
Perhaps the first celebrity appearance was in 1928, when Walt Disney himself provided the voice for Steamboat Willie, widely regarded as the breakthrough for animation.
And although there were celebrities in the late 1960s and early 70s who voiced the characters in animated features - think Louis Prima and Phil Harris in The Jungle Book - the gold rush began when Robin Williams took over the role as the big blue genie in Disney's Aladdin.
Mel Gibson, Chicken Run
Ellen DeGeneres, Finding Nemo
Jennifer Saunders, Shrek 2
Woody Allen, Antz
Kevin Spacey, A Bug's Life
Ray Romano, Ice Age
That was in 1992, the year after Beauty and the Beast became the first animated feature to be nominated for Best Picture at the Academy Awards, and when the modern golden age of cartoons began.
Tim Allen and Tom Hanks followed suit in Toy Story, voicing Buzz Lightyear and cowboy Woody; John Goodman and Billy Crystal voiced working-class sidekicks Sulley and Mike in Monsters, Inc.
Not, er, realistic?
While audiences might enjoy listening to their favourite actors, not everyone thinks the trend is a good thing.
In 1998, when DreamWorks released Prince of Egypt - starring the voices of Sandra Bullock, Michelle Pfeiffer, Ralph Fiennes, Helen Mirren, Steve Martin and others - movie critic Leonard Maltin told the Chicago Tribune that he was concerned about the star power behind the cartoon characters.
"I don't want to be thinking of Michelle Pfeiffer and Sandra Bullock," he said.
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"I just want to be lost in the story and the characters. If they do their job, I will be, but I think it creates more of a challenge when you have such big star names doing the voices, instead of just getting the best voices for the part."
Mr Kemp says Jeffrey Katzenberg, who set up DreamWorks with Steven Spielberg, actively recruits stars for animated films because he "takes them very seriously". The studio's upcoming projects include Shark Tale, with the voices of Will Smith, Robert De Niro and Renee Zellweger.
And cartoons do serious business: Pixar Animation Studios' Finding Nemo was the top-grossing film of 2003. It also won the Oscar for best animated feature.
Money money money
Besides the cachet of being in a hit film, there's also cash in it for the actors. The three stars of Shrek 2 made $10m each for voicing the roles, according to industry publications.
But Mr Kemp says the reason actors lend their voices to cartoon roles is very much the same as how they decide on their usual roles.
"If Jeffrey Katzenberg is making an animated feature and he calls you up and you're a star, you'll pretty much do it.
"It's the same rules that apply to animation that apply to anything else. If the script is good, and the agents want their actors and actresses to be in it, then they will do."