Dr. Shreek as he appears in the TV episode.

Beautiful hands!
~ Dr. Shreek about Jerry's hands.

Dr. Shreek is Jerry's piano teacher and the secondary antagonist of the Goosebumps book Piano Lessons Can Be Murder. He is a creepy Santa Claus lookalike who seems a little too obsessed with Jerry's hands. After Jerry decides to quit his piano lessons, Dr. Shreek flies into a rage and chases him through the piano school, where Jerry discovers pianos played by disembodied human hands. Mr. Toggle saves Jerry by showing him that Dr. Shreek is actually a robot, and shuts him down before revealing himself to be the true villain of the book.