Shrek 2: Andrew Adamson felt a bit artistically constricted on Shrek 2. A co-director on both Shrek movies, Adamson felt he and his collaborators wrapped up the 2001 original too neatly, making it tougher to develop the sequel.

Adamson's main beef: He wishes they had not let Shrek and Fiona marry at the end of the first film. The filmmakers could have strung out the romantic mayhem in the sequel if the two had yet to tie the knot, Adamson said.

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"But it actually forced us to push the story through more twists and turns and prevented us from letting the film fall back into sequel cliches," Adamson.

Among the twists: Turns out Shrek wasn't the fairy-tale true love meant for Fiona, after all. A guy named Prince Charming was (Rupert Everett (news) provides the voice of the unlucky-at-love prince).

While the filmmakers had not been thinking sequel on the first "Shrek," they have left more leeway to continue the story after the new installment, Adamson said.

"This time at least, we're preparing for it. We're trying not to make the same mistakes," Adamson said. "In the first movie, Shrek learned he could be lovable to some degree. This movie, he learns how to love, and at some point, he needs to learn to love himself. So there is still more to be told about these characters. They still have room to go."