Jonny Quest is an 11-year-old boy. After losing his mother at an early age, he accompanies his scientist father on extraordinary adventures.

Dr. Benton C. Quest is a scientific genius who works for the U.S. Government. He is considered "one of the three top scientists in the world", with interests and technical know-how spanning many fields.

Bandit, Jonny's pet bulldog, is unique among his fellow Hanna-Barbera dogs in that he is a regular non-anthropomorphic dog. Still, he seems uncannily able to understand human speech and is capable of complex facial expressions.

After the death of Dr. Quest's wife, Intelligence One assigned agent Bannon to guard Jonny "twenty-four hours a day as tutor, companion, and all around watchdog."

The Quest family has a home compound in the Florida Keys (on the island of Palm Key) but their adventures take them around the world.

Although most villains appear in only one episode, the Asian criminal mastermind known as Dr. Zin is a recurring nemesis. With yellow skin and a maniacal laugh, Zin is an example of the Yellow Peril villains common in Cold War-era fiction.

The seventh son of a seventh son, Jonny's best friend and adoptive brother Hadji seems to possess mystical powers (including snake-charming, levitation and hypnotism), which may or may not be attributed to parlor trickery.

Hadji frequently uses "Sim Sim Salabim" as his incantation while performing "magic" (or at least some pretty good stagecraft) to get him and Jonny out of a tight spot.

In "The Mystery of the Lizard Men", a freighter in the Sargasso Sea is destroyed by a red beam of light and Team Quest is called in to investigate. Although the culprits at first seem to be lizard men, Dr. Quest uncovers a more plausible explanation--foreign mercenaries in lizard suits.

After an accident, test pilot Jud Harmon was rebuilt into Skyborg by a foreign power. The cybernetic implants turned him against humanity, until he was saved by his old friend, Race Bannon.