 " It 's About Time ! " is the twenty @-@ first broadcast episode of the animated television series Phineas and Ferb 's first season . It originally aired on Disney Channel on March 1 , 2008 . The episode concerns stepbrothers Phineas and Ferb fixing a time machine on display in a museum and using it to travel back to prehistoric times . Meanwhile , Perry the Platypus deals with being replaced with a panda bear as the nemesis of the mad scientist Dr. Heinz Doofenshmirtz . 
