|First appearance:||April 27, 1990|
|Last appearance:||May 5, 1990|
Mr. Lockjaw is the gym teacher and coach of the baseball team at Calvin's school. He is a squat, burly man with little patience for people like Calvin who lack a competitive spirit. When Calvin leaves the baseball team, Lockjaw calls him a "quitter." This emotional trauma leads to the reader's first encounter with Calvinball.
Before Mr. Lockjaw there was another gym teacher. He only made one appearance in Calvin and Hobbes. He is simply wearing a shirt that says "Gym Intructor". This could mean that the other one was fired or quit. Another Theroy is that there is 2 gym instructers in the school. Mr. Lockjaw has made an appereance in the book Scientific Progress goes Boink.