Candace realizes that she needs to spend more time with Stacy, so she vows to devote a whole day just for her. But while visiting Jeremy and his mom, 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, making it difficult for Isabella to get Phineas out for a movie date.