Phineas and Ferb are in their backyard, trying to make today the sunniest day ever. While they climb back down the tree, Ferb accidentally knocks a bird's egg out of its nest, and it rolls all the way down to rest at Perry's foot. Phineas spots it and concludes that Perry has just laid an egg! However, when they both turn around, Perry is gone. He enters his lair. Phineas and Ferb build a contraption, called the Platydroid, that warms the egg and plays Perry's chattering noise at any time to keep the egg safe. They were supposed to build the whole thing as a platypus, but they thought it would take too much time, so they built the bottom half only (the Platy-posterior) instead. Phineas states that nothing says mother's love like a giant robotic platypus butt.
Inside their house, Candace is watching a show about sea turtles. She is eating popcorn and in the show, it says that even if the turtle cannot even walk five feet, it still has a chance of danger. This has an emotional effect on Candace. She opens up the window and sees Phineas and Ferb helping the egg. She runs out and holds the egg. Candace says that the egg needs a mother, so she runs back inside the house and comes out wearing a platypus suit, claiming natural maternity will be more helpful to the egg than their technological platy-posterior.
Mother Nature Won 2
Candace talking to Phineas and Ferb in Technology vs. Nature.
Meanwhile, Perry meets Doofenshmirtz out in the ocean. He sees Doofenshmirtz throwing a bucket of krill out in the water, and finds out that Doofenshmirtz used to love a girl who loved whales, and since he loved her so much, he invented a Whale-Translator-inator. However, the whale told the girl that she should dump Doofenshmirtz and go out with him. She follows the whale's orders, leaving Doofenshmirtz with a broken heart. He decides to put his "evil plot" into action: revenge on the whales by speaking a whale song out in the ocean to insult them.
Perry does not believe Dr. Doofenshmirtz is doing anything evil and flies off, leaving the mad scientist chasing after him, totally forgetting about his plan at all. He constantly tells Perry to thwart his plan, even by trying to point out very crude parts of his plan, but it just seems to be scaring Perry away.
Phineas and Ferb close the contraption they made, and Ferb pockets it. They then build Candace a rack of clothes and other materials for her to lay on top on with the egg. The egg hatches, but a platypus doesn't come out. Instead, a rare "Whale song-singing double-breasted angle hooper" emerges and Ferb states that the bird is the natural enemy of the platypus in the wild. Since Candace is wearing a platypus suit, the bird begins to attack her.
Linda comes over and says that Candace shouldn't have made Phineas and Ferb build her a mass of blankets and objects just to watch a bird egg hatch. She leaves with Candace trailing her, complaining about after missing all the boys' projects the only one Linda sees is hers. Jeremy suddenly enters the backyard inviting Candace somewhere, but makes an awkward pause when he sees her still in her mom suit; Candace brags to Linda because Jeremy understood what she was doing.
At the end, Doofenshmirtz blasts off and gets his head stuck in the blowhole of a whale. Inside, he sees his old girlfriend cooking. She says that dumping him was the best decision she ever made.