"The Monster of Phineas-n-Ferbenstein" is the 40th broadcast episode of the animated television series Phineas and Ferb. The episode revolves around Phineas Flynn and his step-brother, Ferb Fletcher, being told the story of how their Victorian ancestor helped a scientist create a monster. Meanwhile, Perry the Platypus is told a similar yet connected story concerning Dr. Heinz Doofenshmirtz's Victorian ancestor, who transformed himself into a monster.