Despite being a robot, Olga has a strong sense of loyalty and duty, which gives her a nurturing, almost mother-like quality. As such, she's perfectly cast as a robot caretaker and/or assistant that displays an undying loyalty to her charge.
Being basically a weapon in rock-giant-form, Garon is pretty stoic. In fact, you might even say that Pick is really the key to his heart. However, when Pick's not there to guide him, Garon is emotionally cold and distant - perfect for him to be cast as a giant space monster adversary for Tezuka's heroes, Astro Boy and Magma.
An inferior copy, created by Dr. Ochanomizu as a temporary replacement for Astro Boy, Cobalt has abilities comparable to those of his brother. However he lacks Astro's intelligence and common sense and is often clumsy, gullible, and accident-prone as a result. Although he often causes problems for the entire family, he remains extremely kind-hearted and loyal - characteristics which help Astro out of trouble from time to time.
Astro's Father was created, along with his much more famous wife, Mitchy, by Dr. Ochanomizu to act as Astro Boy's robot family. Although he is a father figure, as a robot he is actually younger than Astro, and thus attends the same school in a lower grade - something which often leads to some comedic results.
Uran is Astro Boy's tomboy-ish younger sister. She was created for by Dr. Ochanomizu, along with Astro's Father, his mother Mitchy, and his older brother Cobalt, in order to give Astro a more realistic childhood. However, because she was made by Dr. Ochanomizu and not Dr. Tenma, she is not nearly as sophisticated as her older brother and lacks his special powers. However, her jealousy of Astro and desire to prove herself sometimes leads to her disguising herself as her brother in order to have adventures of her own... usually with unfortunate results.
Mitchy was Tezuka's earliest important female star, and is one of the women who appears in the greatest variety of roles in Tezuka's work. Although she monopolized many of Tezuka's early female roles, she was a true student of her craft and proved early on that she was more than just a pretty face - leaving all the "cutey girl" roles instead for Riiko.
Ongoing Serial: a series of episodes, published over a span of weeks/months/years where the story plot is connected from chapter to chapter and must be read in chronological order for it to be understood properly.
Chapter Serial: a series of episodes, published over a span of weeks/months/years where the story plot is self-contained to a single chapter. There may be an overarching plot, but the stories can generally be read in any order and be understood
Book: an all-in-one self contained story published as a one-off.
Supplement: an an all-in-one self contained story published as a stand-alone supplement to a regular weekly/monthly periodical.
Short Story: an all-in-one, self contained story that was published in a regular weekly/monthly periodical
Anthology: a collection of all-in-one, self contained stories that were published in a regular weekly/monthly periodical but are generally grouped together.