Perry the Platypus

Perry the Platypus, codenamed Agent P, is the pet platypus of Phineas Flynn and Ferb Fletcher. Unbeknownst to his owners, he lives a double life as a secret agent for The O.W.C.A. (a.k.a. "The Agency"), a government organization of animal spies. In the Agency, his immediate superior is Major Monogram. Perry has a lair under the Flynn-Fletcher's house that can be entered through various passages. One example is the Chimney Vator, in which he once encounters Santa Claus.

His nemesis is Dr. Heinz Doofenshmirtz. Perry's mission is almost always foiling the doctor's plans, which he successfully accomplishes almost every time even with minimal details about the plans. During these missions, his battle with Dr. Doofenshmirtz cleans up what Phineas and Ferb have been working on that day.