I need your hands, Jerry! To make beautiful music. Hands are just too hard to build--too many moving parts! I...need...your...hands! They're EXQUISITE!!!!
~ Mr. Toggle as his true colors are revealed

Mr. Toggle is the main antagonist in the Goosebumps book Piano Lessons Can Be Murder.

He is an inventor who works at a piano school, but seems to have an obsession about hands. While he was first portrayed as harmless but he is later revealed to be something much darker, a serial killer. He is a self dubbed genius in robotics who also has a obsession with creating beautiful music yet seems to lack the ability to create it with his own hands. Shortly after it's revealed that he steals the hands of students to play music as he is incapable of creating robotic hands. He is also the creator of Jerry's piano teacher, Dr. Shreek, who is actually a very lifelike robot. At the end of the book, the ghosts of his former students chase him from the school and he is never seen again. In the TV episode, the ghost haunting Jerry's house forces him to practice the piano for eternity.