- Vincent Martella (Phineas Flynn (voice))
- David Errigo Jr. (Ferb Fletcher (voice))
- Ashley French (Candace Flynn (voice))
- Caroline Rhea (Linda Flynn-Fletcher (voice))
- Dee Bradley Baker (Perry the Platypus (voice))
- Alyson Stoner (Isabella Garcia-Shapiro (voice))
- Dan Povenmire (Heinz Doofenshmirtz (voice))
- Jeff 'Swampy' Marsh (Francis Monogram (voice))
Phineas and Ferb — S1E40
Episode: The Monster of Phineas-n-Ferbenstein
Air Date: 2008-10-17
Runtime: 11 min
Overview
The boys learn about one of Ferb's Victorian ancestors, who helped a scientist create a monster. Meanwhile, Doofenshmirtz recalls the story of his great-great-grandfather Dr. Jekyll Doofenshmirtz.