Phineas and Ferb travel to the future to find a tool that hasn't been invented yet, and run into future Candace. Seeing an opportunity to finally bust her brothers, she follows them back through time to catch them building their rollercoaster, and exposes their antics to her mom. In the process, she accidentally foils Agent P's defeat of Dr. Doofenshmirtz, starting a chain reaction that turns the future into a dystopian society.

The boys are able to create a giant bubble which enables them and their friends to float and view all of Danville from above as Candace tries to bust them while on a practice drive with Mom for her learner's permit. Meanwhile, Dr. Doofenshmirtz tries to gain popularity by singing country and western music and Perry must stop him before the concert crowd submits to his latest invention.