"Doofus Khan! Regent Monogram will have your head!" — Princess Isabella
Princess Isabella is the princess and ruler of the Tri-Province Area under the guidance of Regent Monogram.
The Princess was kidnapped by Doofus Khan in order to prevent Regent Monogram from countering the Khan's attacks. She was later rescued by Phineas and Ferb and fought against Doof's dragon with them. The Great Wall of China was her idea.
The Princess looks just like her modern day descendant She wears a purple, regal dress with a wide dark purple belt around her chest. Around her neck are dark purple xiapei and a black pearl. She wears a pink-and-purple phoenix crown, with a pink bow on it and purple wings, two on each side, with three black pearls dangling from each. She has a purple bow on her head and sandals on her feet.
The xiapei is a decorated, long piece of cloth put around the neck. It is worn by noblewomen and by brides on weddings.