from a cartoon drawn by himself in childhood, which featured living oatmeal. Extraterrestrial life forms: Calvin encounters many extraterrestrial life-forms in the course of the strip, usually during adventures as his alter-ego, Spaceman Spiff. Most of these aliens are non-humanoid, bizarre monsters, but represent Calvin's imaginative perception of Susie, his parents, and teachers. During the story which gave the name to the Weirdos from Another Planet! collection, Calvin and Hobbes encounter a native Martian, who is a small creature with tentacles and eye-stalks. In the strip's final year, Watterson drew two stories involving recurring alien characters, Galaxoid and Nebular, to whom Calvin "sold" the Earth for 50 alien leaves to use for his science project, which he failed when his teacher rejected the leaves' origin. The donors returned in the final two weeks of strips, angry at Calvin for failing to reveal the changing seasons; but were placated when Hobbes clad them in Christmas stockings. Doctor: Calvin occasionally visits his pediatrician, who appears to be a mild-mannered physician with a friendly demeanor. Calvin, however, sees him as a vicious, sadistic interrogator, sometimes imagining him as an alien or overreacting to playful diagnoses. The doctor made his final appearance when he diagnosed Calvin with chicken pox; he comments on the ability of a virus to "take the edge off a kid", as the illness has left Calvin without the energy to put up a fight. Principal Spittle: Calvin's school principal usually makes his appearance when Calvin has upset Miss Wormwood; typically, he is seen looking over his desk as Calvin tries to explain his latest mishap, with an apathetic or infuriated expression in his face. He is seldom shown speaking except in his first appearance. He is depicted thinking to himself that he hates his job. Mr. Lockjaw: 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, and no sympathy for Calvin whenever Moe gets violent with him in gym class, with Calvin commenting that Lockjaw thinks "violence is aerobic." He does not stop Calvin's baseball teammates from abusing and teasing him, and when Calvin leaves the team, Lockjaw calls him a "quitter". This emotional trauma leads Calvin to create Calvinball, supposedly the least organized sport. Scouts: Early in the strip, Watterson shows Calvin participating with other children in Cub Scout activities in the woods. Watterson