Phineas and Ferb - Season 3 - Eps 22: That's the Spirit
It's Halloween night and the kids encounter a strange boy named Russell who is convinced his house is haunted. Meanwhile, Dr. Doofenshmirtz's disdain for grass causes him to invent a "mind-transfer-inator" enabling him to merge minds with a cow and destroy all the grass in the Tri-State Area. Unfortunately, his plan backfires and he transforms into a scary "were-cow" that wreaks havoc any time there is a full moon. It's now up to Agent P to stop him and save Danville.
About Phineas and Ferb

Title: Phineas and Ferb
First Air Date: 2007-08-17
Last Air Date: 2025-06-05
Status: Returning Series
Rating: 7.9/10 (from 907 votes)
Language: EN
Seasons: 6
Total Episodes: 246
Network: Disney XD Disney Channel
Genres: Animation, Comedy, Family, Sci-Fi & Fantasy
Production Companies: Disney Television Animation
Synopsis
Each day, two kindhearted suburban stepbrothers on summer vacation embark on some grand new project, which annoys their controlling sister, Candace, who tries to bust them. Meanwhile, their pet platypus plots against evil Dr. Doofenshmirtz.
Cast

Vincent Martella
Phineas Flynn (voice)

David Errigo Jr.
Ferb Fletcher (voice)

Ashley Tisdale
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)