Calvin's doctor is a man who's around 40 years old, and by appearance reminds us a little about Calvin's father.
The doctor is the only person that Calvin really fears! (Except maybe for Rosalyn...) This is because he is convinced that the doctor will torture him with all his strange medical equipment. His fear often becomes so great that he defends himself with all means.
Each time he has to visit the doctor he is so nervous that he repeatedly asks about what all instruments are for and what is going to happen to him. Not seldom is the doctor accused of being a quack. Calvin also wonders if he has paid his malpractice insurance, as the little kid is going to sue him for all that he owns! Written evidence that the doctor has passed his exam is also one of Calvin's demands before the treatment can begin. Calvin strongly suspects the doctor of being a direct descendant from Frankenstein. The doctor is totally fed up with the little trouble maker, and probably wishes that Calvin would never get ill!