Phineas and Ferb try to find a way to make everything fun, starting with their house.
Meanwhile, it's Dr. Doofenshmirtz and Perry's 100th battle, and the O.W.C.A. has set up cameras all over Doofenshmirtz Evil Incorporated. Unbeknownst to either Doof or O.W.C.A., Perry has accidentally been switched with an ordinary platypus from the zoo.
- The Cameo: Suzy and Jenny get a non-speaking one at the pet wash.
- Metaphorgotten: "I see what you're doing! You're messing with my head, trying to get into my mind, walk around in there, rearrange the furniture, maybe repaint the kitchen..."
- Out-of-Character Moment: The sole purpose of Dr. Doofenshmirtz' inator, the "Least-Likelyinator".
- Red Eyes, Take Warning: Averted with the platypus from the zoo. It has red eyes so that it can be distinguished from Perry while he's in pet mode, but other than that it's just a regular platypus. However, Dr. Doofenshmirtz might tell you otherwise.