At a recent a press conference for DreamWorks' next CGI animated film Madagascar, DreamWorks' co-founder Jeffrey Katzenberg gave away a very full plot synopsis about what people should expect from the film scheduled to come out in May of 2007 and Coming Soon has the details:

"When 'Shrek 3' opens, Shrek and Fiona are having to take on the duties of being the active king and queen of Far, Far Away. When we left him, the King was quite literally croaking. They're not very comfortable in these roles, so the King says to them, "If you can find the heir to the throne and bring him back, the Kingdom will be in good hands, then you can return to swamp and live your lives." Which is what they want to do. Shrek, Donkey and Puss go to the far side of the Kingdom of Far, Far Away where young "Artie", who is the nephew of Queen Lilian, is about to graduate school.

Artie turns out to be young King Arthur and Shrek and Donkey and Puss have to convince this extremely rebellious young man, who's being voiced by Justin Timberlake, to come back and assume the throne. Along the way, Shrek invents the Round Table, chivalry. Donkey is the Lady in the Lake with the sword. You get it. Meanwhile, back at the Kingdom of Far, Far Away, Prince Charming decides that it's time for a coup d'etat. "The cat's away. He will play" So Fiona organizes all of the princesses into the underground Resistance movement, who are trying to hold things together until Shrek, Donkey, Puss and young King Arthur return."

Thanks to 'Phillippe'