 While working on the animated television series <unk> 's Modern Life , Phineas and Ferb co @-@ founders Dan Povenmire and Jeff " <unk> " Marsh utilized several recurring elements in the episodes that they wrote . Among these were actions sequences and chase scenes . Povenmire and Marsh wanted to reuse these elements in their series and chose Perry to execute it . The pair gave him a consistent and continuous nemesis in the form of Doofenshmirtz as a means of allowing viewers to get to know him . 
