All of the primary characters of the show are members of the Planet Express crew: Fry, Leela, Bender, Professor Farnsworth, Hermes, Dr. Zoidberg, and Amy. Out of these, Fry, Leela and Bender are considered major primary characters, as any of the three are the center of most episodes, and they are the three characters that have appeared in all episodes. Some also call the Planet Express ship a main character, as it appears in all episodes, in spite of having only two speaking roles.[3ACV06][4ACV03] Only two members of the Planet Express crew are not in the main cast: Scruffy and Nibbler.
All in the current main cast were introduced in the first two episodes: Fry, Leela, Bender and the Professor were introduced in "Space Pilot 3000", and Amy, Zoidberg and Hermes were introduced in "The Series Has Landed". The writers have since commented that it wasn't easy to introduce three major characters in a single scene.