Vanessa tries to get her dad, Dr. Doofenshmirtz, a capsule containing a rare chemical in the Superduper Mega Superstore in order to convince him that she's responsible enough to have her own car. Even with Ferb helping her, what initially seems an easy task becomes complicated when Candace, Stacy, Buford, Baljeet and Perry also try to get the capsule for their own purposes.