Phineas and Ferb Season 4 Episode 21 - One Good Turn Episode Title: One Good Turn Episode Description: Motivated by a movie with a strong heroine and also sibling-rivalry, Candace and Stacy feel empowered to team up against rival groups and compete in Phineas and Ferb's Ultimate Obstacle Course. Across town, Doofenshmirtz plans to humiliate his brother, the Mayor, by using his 90 Degree-turn-inator on him so that he will accidentally insult the Mayor of Stumblegimp and be forced to perform the shameful "Dance of Contrition" to make amends.