Skeleton King is the main antagonist of Super Robot Monkey Team Hyper Force Go!. He is a deeply corrupted individual, having been directly exposed to large concentrations of Dark One energy in life. After assuming the form he takes at the beginning of the series, he swears dominion over Shuggazoom, with the intent of making all of its citizens subservient to him, and raising an army of the undead to continue his conquest upon the universe itself.
The Skeleton King continually antagonizes the monkeys for the first two seasons, before being killed by Antauri in the Season 2 finale. The Dark One Worm assimilates his skull, enabling him to live on as the beast's vessel. After the worm is destroyed, his skull changes hands continuously before being obtained by Valeena and Mandarin, who successfully manage to resurrect the Skeleton King in a new, more frightening form.
Throughout Season 1 and 2, The Skeleton King has the appearance of a stylized skeleton with a blocky, jagged skull and a robust, partially mechanical body. The Skull has a small horn on top and two jagged ear-like appendages on each side. It also has some minor damage including a small crack above his left eye, and a larger one going from the top of his nose hole to the top of his head. His torso and arms are a bluish purple, while his arms and legs are clothed in dull red coverings. His legs are clothed in a grey-brown pair of pants with ripped cuffs, and a cowl-cape is wrapped around his neck, and hangs from his shoulders.
His torso has a prominent breast plate adorned with a white crest, which itself has a small indentation that is occupied by Skeleton King's Third Eye. His abdominal organs are completely exposed and are a notable weakpoint. They appear to vaguely resemble human organs at most, and are vibrantly coloured. His arms appear mostly mechanical, with shiny, glossy exteriors and metallic inner parts.
When possessed by the Worm, Skeleton King's design remains mostly the same, however his face is covered by purple nerve-like growths that travel into his eye sockets, which now glow a solid colour. He retains this appearance even after being decapitated by Chiro. During the destruction of the Worm, Skeleton King's skull would incur battle damage in the form of claw-marks, and would remain this way even after being severed from the worms.
In the episode, Secret Society, his skull is, at on point sent violently crashing around the room, which causes it to crack open and shatter, revealing a second, more humanoid skull beneath. It appears to be made out of crystal according to words from the other characters.
Finally, during the episode, Soul of Evil, Skeleton King is properly resurrected by Valeena, Mandarin, and a brainwashed Sparx. His new form is considerably different. He now possesses a more solid-looking body with a black body suit, decorated with light blue stripes, as well as light-blue gloves and boots. His old cape is instead replaced by the Alchemist's robe, and his head is adorned with a helmet featuring the same crests as his previous skull. His voice is notably raspier in this form than his previous one.