Day of the Living Gelatin

Candace's gelatin party inspires Phineas and Ferb to create the biggest gelatin mold ever in Isabella Garcia-Shapiro's swimming pool. Heinz Doofenshmirtz invites Perry the Platypus over for tea in order to convert him to an evil ally, "one way or another". Thanks to Doofenshmirtz's invention, he accidentally turns the gelatin into an evil monster.