Phineas and the gang celebrate Isabella's birthday in a big way, but all she really wants is some quiet time with Phineas. Meanwhile, Doofenshmirtz has installed his Bugs Me-Inator onto an evil bug bus and is driving around Danville turning all the things that bug him literally into bugs.

Candace and Stacy compete in Phineas and Ferb's Ultimate Obstacle Course. Doofenshmirtz plans to humiliate his brother, the Mayor.