When Phineas and Ferb find an egg, they believe it belongs to Perry, so they build a mechanical contraption to care for it. When Candace sees what her brothers are doing, her maternal instincts emerge. Meanwhile, Doofenshmirtz plots revenge on whales who told his girlfriend to dump him by means of a whale translation device he created.
Phineas and Ferb create their own video game and program themselves into it. When Candace is accidentally zapped into the game, Phineas and Ferb have to bring her back in time for her cotillion.