The series features the following four main characters throughout its run:
Captain Caveman, or "Cavey" for short (voiced by Mel Blanc), is the protagonist of the show, billed as "the world's first superhero." He is a caveman who is millennia old (his exact age is never disclosed, although in an episode he is carded by a doorman who is unsure Cavey is old enough to let in, to which Captain Caveman responds, "I'll be 2 million next month."). He can pull various objects from his long body hair that covers his body except for his nose, arms, and legs. He can also fly, but his flying power always seems to fail him at the worst possible moment. Sometimes he would attribute this mishap to an energy shortage ("Uh oh! Bad time for energy crisis." CRASH!), which was a reference to the gasoline rationing shortages of the late 1970s. He speaks in stereotypical "caveman-talk", replacing subject pronouns with their object equivalents and dropping articles such as "the" (for example, "Me know where bad guys are hiding."), and often mumbles the nonsense phrase "unga bunga". He also has a bad habit of occasionally eating large non-food objects in one gulp (e.g. bicycles, TV sets, safes, table lamps), and the Teen Angels occasionally have to stop him from eating potential clues that will help them to solve the mystery. Despite this, Cavey is ultimately loyal to them and he is very capable capturing culprits.
Dee Dee Skyes (voiced by Vernee Watson) is the brains of the Teen Angels. Dee Dee and the rest of the Teen Angels found the frozen Captain Caveman and defrosted him. She wears her hair in an afro and usually wears a red turtleneck sweater with a blue skirt and red knee high boots. Both her dress style and her knack for solving mysteries make her similar to Velma Dinkley of Scooby-Doo fame, while she also bears a resemblance to Valerie from Josie and the Pussycats. She is misidentified as Brenda in the opening credits. Though some sources give the family name of both Dee Dee and her uncle Frank as "Sykes", their name is given as "Skyes" in the episode "The Fur Freight Fright", which featured Frank and his company "Skye's Furs". Her adaptation in the 2020 film Scoob! as Blue Falcon's assistant (voiced by Kiersey Clemons) also introduced herself as Dee Dee Skyes, and she is listed as such in the closing credits.
Brenda Chance (voiced by Marilyn Schreffler) is a nervous brunette who is always scared of the demons, monsters and phantoms that she encounters and always tries to back out of a scary mystery similar to that of Shaggy Rogers, but always ends up getting captured or the short end of the stick. She wears a purple striped tank top and a pair of hot pink flared trousers with a white belt. She is misidentified as Dee Dee in the opening credits.