Gelatin monster

The Gelatin Monster was created by Phineas and Ferb, actually first it was a normal gelatin in Isabella's pond, but when Doofenshmirtz's Evil-inator hits it, it becomes a monster. It ate Candace and Jeremy's gelatin sculpture as they sung Come On, Kids!, because they wanted to kill it by throwing it water. Then Doofenshmirtz call it and became his sirvant to destroy Perry the Platypus, but with water it was killed. Doofenshmirtz cries as the monster is killed, so it means he appreciated it as his son ("Day of the Living Gelatin").