When Phineas and Ferb discover a commemorative coin from the 1903 Danville World's Fair, Lawrence recounts the events of the festival to them, in which steam-driven devices were introduced and a set of kids, who were very much like them, were preparing for the highly anticipated event.

Annoyed at waiting in really long lines at the return counter, Doofenshmirtz invents a "Back-to-the-Store-inator" to send things back to the store where they came. Meanwhile, Phineas and Ferb stage an extreme batting challenge their friends take place in, and Candace's obsession to bust coincides with her and Jeremy's visit to the Extreme Water Park.