In "Shrek the Third," Shrek faces new challenges as he learns that he must become king of Far Far Away after the death of Fiona's father, King Harold. Reluctant to take on the royal responsibilities, he sets out on a quest to find the rightful heir, Arthur, who is a teenager and not quite ready for the throne. Meanwhile, Fiona and her friends, including Donkey and Puss in Boots, work to defend their kingdom from the scheming Prince Charming. The film explores themes of friendship, responsibility, and the importance of being true to oneself while delivering humor and adventure.