The Six (unofficial group name) are a group of six individuals that survived the destruction of Kingdom Cum (due to the Choomah outbreak). They haven't been mentioned much in the series, but they're hidden throughout the show and occasionally reveal themselves.
The theories of the survivors began after Choomah Island. Bumble Brutus had confronted Lez, who had just revealed that he's planning to go back to Kingdom Cum to face his father and take the throne that is rightfully his. Bumble Brutus then reveals to Lez that Kingdom Cum has been destroyed. He then says that he's surprised that six Kingdom Cumians survived. This meant that Lez and his brother Norton were two of the last living Kingdom Cumians left in universe.
For a long time, Lez and Norton were the only known survivors of Kingdom Cum. However, in the finale of Season 2, the third survivor was confirmed; Lez and Norton's father, King Larrinox, the former ruler of Kingdom Cum. Larrinox appeared in a spaceship, saving Cecil the Sasquatch from his vengeance seeking son, Lez. During his reveal, Larrinox further angered Lez by placing Cecil's claim as King of Kingdom Cum before his own, despite the fact Lez is a Kingdom Cumian (Cecil is not), he is the rightful and official heir, and also the fact he is a member of the royal family.
The rest of the list was partly confirmed within the final two episodes of Season 3; Potadahead and Choomah Island 2. In Potadahead, Clarence was confirmed to be the fourth survivor, as well as the accidental creator of the Choomahs. Clarence reveals that he was the greatest and most loved scientist on Kingdom Cum until his formula to create super soldiers (secretly ordered to create by King Larrinox) was sabotaged, turning him into his disfigured potato-looking form. Without knowing it was him, his fellow scientists threw him into an emergency shuttle and, along with the Choomah formula that could reverse the Potadahead effects, blasted him into space.
Coincidently, this happened around the same time that Lez and Norton were banished by their father, King Larrinox, for wrecking Horizon's End city the night before the revealing of the new King, since they'd both spiked each other's drinks to sabotage the other's chances of becoming the King. An even bigger coincidence is that Clarence's exile from the planet also took two days - Lez and Norton were banished the next day - before the Choomah outbreak that destroyed Kingdom Cum, causing the incident to indirectly save Clarence from what would've been certain death.
In Choomah Island 2, the final two survivors were partly confirmed: Ellis and Sergio Warnington (possibly, still unconfirmed). In a fight between Ellis and Cecil, Ellis openly admits that he's not a human being, before beating his foe by using super inhuman abilities and the power to fly. When a wounded and battered Cecil demands an explanation, Ellis finally reveals himself as one of the Kingdom Cumians that survived, which means that, due to being his cousin, Sergio could be too.
However, Ellis is able to fly and jump long distances, whilst the other survivors (Lez, Norton, Clarence, possibly King Larrinox) cannot. This might suggest that Ellis is a rare and powerful breed of Kingdom Cumian, and therefore the last of that breed.
Choomah Island 2 therefore answers the whole list, but also alters it too. During the episode, Norton is killed by a vengeance seeking Lez, eliminating him from the list. Clarence is unconfirmed whether he's dead or alive, most likely alive due to his ability to heal any wound or injury, which makes the list more like 'The Five'.
Futhermore, Sergio's place on the list is up for debate as he has never demonstated any kind of the superhuman traits that Kingdom Cumians are known to possess. Such traits include super inhuman strength, the ability to survive extreme wounds, and prolonged life expectancies. Other Kingdom Cum survivors - Lez, Norton, King Larrinox, Clarence, Sergio's cousin Ellis - have shown these abilities in the past, Sergio has not.
After the events of Choomah Island 2, the full yet still unconfirmed list has been updated:
- Leslie Mackerel
- Norton Sparkles (deceased)
- King Larrinox
- Ellis Warnington
- Sergio Warnington (unconfirmed)