Minor Characters are characters who play a very small role in the show, characters with no names, and characters who are mentioned but not seen.
|K.O. & Dendy's Classmates||"I Am Dendy", "Mystery Science Fair 201X" and "The So-Bad-ical"||K.O. and Dendy's Classmates are, as the name suggests, the classmates of K.O. at Original County Public School. Two of them are officially named- Nanini and Genesis.|
"One Last Score"(Lumpy)
|These two are both people who have mechanical arms.|
|Ms. Mummy's Mother||"Parents Day"||She looks like a human with a lion's tail, which is very different than her daughter. However, they both have an Ancient Egyptian motif.|
|Drupe's Mother||"Parents Day"||She looks like an orange with a business woman-like outfit and has a purse that resembles a slice of watermelon. It is not known why she and her daughter are not the same kinds of fruit, as Drupe is a Strawberry.|
|Brandon's Parents||"Parents Day"||They both bear resemblance to the Hanna-Barbera characters Yogi Bear and Cindy Bear.|
|Rain Cloud||"You're Level 100!"||Small rain cloud with a briefcase. He rained on K.O.|
|Kappas||"No More Pow Cards"||One of the unknown Kappas is level 0.1, making this character the only one in the series so far to have a decimal as their level, besides K.O.|
|Animals in Human-Suits||"We've Got Fleas"||They are all animals that wish to be humans and wear human-like clothing and disguises to fit in.|
|Blue Guy in a Tie||"Plaza Prom"||He wears a small yellow tie while the rest of his body is blue. He currently has no name, and has had no lines in the show so far.|
|Doctors||"Plaza Prom" (Male)
"Know Your Mom" (Female)
|They are humans who help those in need of medical assistance.|
|Small Purple Cat||"Plaza Prom"||He is a small purple cat who appears in the crowd at the plaza prom.|
|Blorp Fandom||"Everybody Likes Rad?"||The man with the "Rad Dad" shirt is voiced by Dave Herman, the lady with the "le Blorp" shirt is voiced by Melissa Villasenor, and the zombie-like fans are voiced by Ben Jones.|
|Cast Crew||"Everybody Likes Rad?"||Two Crew Members who work with The Director. One of the cast crew members have lines, while the other doesn't. The Cast Crew has unknown names.|
|Party People||"We've Got Pests"||People who came to Gnarlio's party at the bodega.|
|Puck Reverie's Mother||"Parents Day"||Mother of Puck Reverie and the sister of Bernard. She is described as a lady wolf-man, and was previously married to an angel. Her fur is purple, much like her brother's.|
|Succulentus's Grandson||"Know Your Mom"||Grandson of the former villain Succulentus.|
|Unnamed Wizard Villain||"Know Your Mom"||He fought against Silver Spark once.|
|Imaginary Villain||"Know Your Mom"||Villain imagined by K.O. when he wanted to find Carol a new super villain to battle.|
Prostratum is a former member of the Kaktus Krew who is mentioned by K.O. in the episode, "Know Your Mom". The way the scene plays out when K.O. tries to call Prostratum, it seems as if they passed away.
It is unknown who K.O.'s father is, but he has been mentioned by K.O. and Carol many times, like in "Know Your Mom", and "Let's Have a Stakeout". He currently has no name, no appearances, and no lines in the show. In "My Dad Can Beat Up Your Dad", Carol claims he was a great man and a great hero, and that he would have loved K.O. very much.