Perry wants to destroy footage from a traffic camera to keep his identity a secret, as Candace tries to use the film in hopes of proving her brothers create unusual stuff. Then, the guys decide to build the largest bowling ball and pins in the world, while Doofenshmirtz wants to rid the world of rainbows.

Candace realizes that she needs to spend more time with Stacy, so she vows to spend the whole day with her only. But while visiting Jeremy and his mom, Mrs. Johnson, Dr. Doofenshmirtz's "combine-inator" zaps her and Jeremy, literally joining them at the hip. Meanwhile, Phineas and Ferb build a giant robot dog that causes a lot of mischief.