After watching a sci-fi movie marathon, Candace becomes convinced that Ferb is an alien. Meanwhile, Dr. Doofenshmirtz tries to market an evil invention by claiming it to be a cleaning device.

Irving's brother Albert doesn't believe that Phineas and Ferb are anything special, and since he claims to be the "Truth Detector," he can prove it. Desperate to prove Albert wrong, Irving convinces Baljeet and Buford to pose as Phineas and Ferb beside a giant hologram of the boys' Eiffel Tower construction. Meanwhile, Dr. Doofenshmirtz is fed up with the quality of accessories for his model train set, and decides to shrink down a variety of national monuments to add to his collection.