At first glance, Perry seems like an ordinary platypus who doesn't do much, but in reality, Perry lives a secret life as a secret agent named Agent P who works for The O.W.C.A. (a.k.a. "The Organization Without a Cool Acronym"), a government organization of animal spies. Every day, Perry disappears to recieve a mission by Major Monogram, about the "evil" things his nemisis, Dr. Heinz Doofenshmirtz is up to. 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. Doof once asked Perry if he liked him, until killer pizzas cam along. Perry then tried to stop them only ended up eating them. Doof tried to ask him again if he liked him, and Perry burps in reply.
Although Perry doesn't speak, the chattering noise which he makes is voiced by Dee Bradley Baker.
Perry has poisonus ankle barbs
He is also the 5th character in the series to burp. In order: Ferb, Candace, Pinky, and Buford
However Perry only burps in the magazine story "Attack of the Killer Pizzas"