Butty "Kent" Butterson is Shelby's little brother and a main character in "Little Brother." He briefly appears in the episode "Bad Timing." He apparently defeated the Rat King. After the events of "Little Brother," Kent returned to what Shelby refers to as "The Underworld" to be with the Dewdrops. In "The Cooler," he appears on one of Princess Bubblegum's surveillance cameras.
Kent is Shelby's butt, but alive. He has black eyes and short, stubby arms and legs. He is pink. He looks a bit like a Scientific Parasite.
Shelby and Kent seem to have a close relationship, as they are both brothers.
- Kent carried a green margarita sword, but it broke after he first tried to defeat the Rat King.
- He's actually Shelby's butt who's come to life, based on the myth that when a segment is cut off from an earthworm both sections can regenerate into two worms.
- However, there is a real species of worm that can regenerate when cut in two, the planarian.
- Kent is Shelby's nickname for Butty.
- Kent having to return to the Dewdrops after partaking in their food is similar to the myth of Persephone and Hades. Persephone is tricked into eating pomegranate seeds from the Underworld and is forced to return every winter.
- Kent's name is based on Adventure Time writer and storyboard artist Kent Osborne.
- Kent's sword, forged by the Dewdrops, is named Punch Party. It is revealed at the end of the episode that Shelby kept it, along with the Rat King's teeth.