The following is an excerpt from studio publicity material, which describes the cast of characters:

Shirley Partridge is the glue that holds the family together. An extremely attractive woman in her late thirties, she is warm, loving and understanding, with a great sense of humor. She can also be a firm disciplinarian when the occasion arises, being the only one who can call a halt to Danny's wild schemes or the brother-sister arguments between Keith and Laurie.

Keith Partridge is 18 and a Senior at Galaxy High School. A handsome boy, Keith is not always as attractive to females as he thinks. It's not unusual for him to have big eyes for a girl who won't give him the time of day. Something of a smart-aleck, he feels quite superior to the rest of the Partridge kids, and is something of a pseudo-sophisicate. The usual object of his sharp verbal digs is his sister, Laurie.

Laurie Partridge is 17, a Junior at Galaxy High. A beautiful girl, she is cool, hip, and will take no sass from her older brother. While it very seldom comes to a peak, there is a certain competiveness between Laurie and Keith, despite the love of all the kids for each other. Whatever Keith's put-down line may be, Laurie can usually come up with a topper.

Danny Partridge is 13, in the 7th grade, and a first-class pain in the butt. Money-hungry and scheming, he always has some big plan cooking, which usually winds up getting him into trouble. Or, quite often, getting the rest of the family into trouble.

Chris and Tracy are the youngsters of the family. 9 and 8, they are always together, and what one does, the other does too. They are cute, curious and fearless, and always in a state of excitement, no matter what may be going on. There is somewhat of a competiveness between them, as Tracy feels that girls are superior, and Chris should follow her lead -- much to his chagrin.

Then there are the Partridges' friends . . .
 

Reuben Kincaid is the Partridge's agent. Something of a bumbler, Reuben often talks when he should be listening, and as a consequence can be found on occasion with his foot in his mouth. A perfect foil for Danny's barbs, he is totally loyal to the Partridges and can be trusted completely, unless it has to do with keeping his mouth shut or giving advice.

Orbit is the Partridge's robot dog, although he refuses to believe he is either robot or dog. Put together by Danny from a $19.95 kit, Orbit is Danny's constant shadow. As usual, Danny didn't exactly follow directions, so Orbit isn't exactly what the plans called for. Danny programmed him to be completely literal, making for problems. A command like "Go straight home!" can be distasterous because that's exactly what Orbit will do -- straight through walls, cars, people, and anything else that's in his way!

Veenie is a Venusian exchange student, and one of Keith's classmates at Galaxy High School. A nervous type, Veenie has the Venusian ability to teleport, de-molecularizing in one spot and appearing in another. This comes in handy for Keith when he is locked out of places he wants to get into.

Marion Moonglow is a friend of Laurie's and also an exchange student at Galaxy High. Cute and bouncy, with very attractive antennae, she is green, which is not unusual for a Martian. Marion has a very pronounced drawl, since she is from Southern Mars, and in moments of stress or high emotion is unable to control her gravity quotient causing her to float upwards till she is stopped by Laurie, or the ceiling.