Phineas and Ferb is an American animated comedy-musical television series. Originally broadcast as a one-episode preview on August 17, 2007 and again previewed on September 28, 2007, the series officially premiered on February 1, 2008 on Disney Channel, and follows Phineas Flynn and his English stepbrother Ferb Fletcher on summer vacation. Every day, the boys embark on some grand new project, which annoys their controlling sister, Candace, who frequently tries to reveal their shenanigans to her and Phineas' mother, Linda Flynn-Fletcher, and less frequently to Ferb's father, Lawrence Fletcher. The series follows a standard plot system; running gags occur every episode, and the b-plot almost always features Perry the Platypus working as a spy ("Agent P") for OWCA (the Organization Without a Cool Acronym), to defeat the latest scheme of Dr. Heinz Doofenshmirtz, a mad scientist driven largely by a need to assert his evilness. Sometimes, other villains scoff at his level of evil. The two plots intersect at the end to erase all traces of the boys' project just before Candace can show it to their mother. This usually leaves Candace very frustrated. Wikipedia
(repeated line) Phineas: I know what we're gonna do today.