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.

Phineas and Ferb's newest invention is a pair of boots that make the wearer extraordinarily fast. Candace decides to wear them so that she can be in two places at once; at Jeremy's family picnic, where she runs into Mrs. Johnson, and also at the library where she promised Mom she would read to the kids. Meanwhile, Dr. Doofenshmirtz's building is put up for sale so he tries to convince a prospective buyer, Annabelle, who turns out to be a long lost relative of the Johnson family, that it is not worth buying.

Candace gets a bad haircut and must rely on Phineas and Ferb's hair growing machine to correct it before she attends the Endangered Animal Benefit with Jeremy and his mom. However, when Candace turns up the power, her hair grows much more than expected and she is mistaken for a rare tangerine orangutan. Meanwhile, Dr. Doofenshmirtz is developing his Very, Very 'Bad-inator.'