Perry the Platypus, also known as Agent P or simply Perry, is an anthropomorphic platypus from the animated television series Phineas and Ferb. Perry is voiced by Dee Bradley Baker and created by the series' co-founders, Dan Povenmire and Jeff "Swampy" Marsh. He first appeared along with the majority of the main cast in the pilot episode "Rollercoaster." Perry is featured as the star of the B-plot for every episode of the series, alongside his arch-nemesis Dr. Heinz Doofenshmirtz.
Perry is the pet platypus for the blended Flynn-Fletcher family, and is perceived as mindless and domesticated. In secret, however, he lives a double life as a member of an all-animal espionage organization referred to as The OWCA ("Organization Without a Cool Acronym"). Many entrances to this organization are usually found all around the house; such as the side of the house, most notably the tree that the boys sit under and many other everyday objects that seem to elude the family's attention. He engages in daily battles with Dr. Heinz Doofenshmirtz, an evil scientist who desires to take over the Tri-state area with obscure contraptions.
Source: Wikipedia, "Perry the Platypus", available under the CC-BY-SA License.