Perry the Mutated Platypus

Day 1 (Perry loses his fur)
Perry, in one of Doofenshmirtz's fights, loses balance and falls in a vat of toxic chemicals. He loses his fur. Linda, unaware of Perry's toxic incident, tells the boys that Perry lost his fur, and therefore needs to wear a protective collar (again). She claims that Perry has gone too far in chasing birds, and landing in wet cement. However, Perry's flashback shows the truth on how he lost his fur. His flashback ends with him in the infirmary, strapped to a bed. Agent E (eagle) gives Perry a mirror to see what has happened to him. Perry chatters in fright.

Day 2 (Perry's side effects)
When Perry woke up for breakfast, his fur grew back. This pleased him. However, due to the radiation in the waste, he had other side effects: he grew very giant, his eyes turned yellow, and he has a change in fur color. Since he grew, he was unable to enter his lair. Because of that Monogram and Cal Karl had to fly to the Flynn-Fletcher residence via helicopter.