The main characters of Norby: The Mixed-Up Robot are Jeff Wells and Norby. Jeff is a student at the Space Academy and hopes someday to join the Space Command and to invent a way for people to easily travel through hyperspace. A good-natured fellow, Jeff sometimes makes mistakes; the novel begins with his being in trouble for disabling the Space Academy's kitchens while trying to have a computer teach him Martian Colony Swahili. He is well matched by Norby, a robot with extraordinary, but hard to control, alien powers. Norby whines a great deal and talks too much, but he has an earnest good nature that makes him likable.

Neither Jeff nor Norby's character is developed in detail, but they are fun to read about, as they try to stop Ing's effort to seize control of the solar system.

Other important characters are Ing...