: This episode introduces Phineas’s iconic catchphrase when he notices Perry has disappeared.
: The invention conveniently vanishes just as Linda arrives, a staple "helpful" plot device usually caused by Dr. Doofensmirtz's antics. [S1E1] Rollercoaster/Candace Loses Her Head
: Phineas and Ferb begin their summer by building a logic-defying rollercoaster in their backyard, setting the "big project" template for the series. : Phineas and Ferb begin their summer by
: Perry the Platypus sneaks off to his secret lair to receive a mission from Major Monogram, marking the first time he foils Dr. Doofensmirtz's "Inator." [S1E1] Rollercoaster/Candace Loses Her Head
(the second half of S1E1) specifically features the family celebrating Candace’s birthday at Mount Rushmore, where Phineas and Ferb attempt to carve her face into the mountain as a "helpful" gift, while Candace nearly loses her mind trying to expose them.