The character that appears in every episode of Phineas and Ferb is Perry the Platypus. Despite Phineas and Ferb being the main stars of the show, Perry is always on the screen. Perry is the pet platypus of Phineas and Ferb, but he is actually a spy known as Agent P, who works for a covert animal organization called O.W.C.A. His mission is to stop the evil plans of Dr. Heinz Doofenshmirtz, who is completely unaware that Perry and his pet alter ego are one and the same.