Platypus monster was a platypus-based monster that was created by Dr. Phineastein and his assistant Ferbgor during the Victorian age. He has a rivalry with Jekyll Doofenshmirtz and supposedly ate him. This is an allusion to Perry and Heinz Doofenshmirtz's daily rivalry. During his journey through town, he passed a man in his underwear who had just announced he was over his fear that a giant platypus would see him dressed like that. He appears to be sane as he ate dinner with Isabella's ansesctor.