"Fault, scratch and choke -- are you trying to hustle me?"
—Mangosteen, Death Screen
Mangosteen is a floating 8-ball that appears in the boss fight with King Dice when landing on Space 8.
He has two rows of teeth acting as a mouth and two eyeballs situated at each end of the mouth.
Mangosteen seems to be quick to jump to conclusions, possibly sometimes not realizing that said conclusions he makes are false, considering his accusation of how Cuphead and Mugman tried to "hustle" him (as shown in his death screen), when in fact they just want him out of the way. He also appears to have a weak stomach (if he even has one), as evidenced by his vomiting, when he is defeated.
Before the battle starts, Mangosteen is basically a faceless 8-ball, but then his eyes and teeth slide over to become a face.
The boss has only one known attack, which is shooting color spectrum orbs from his mouth that aim at the player's position, which can be easily avoided. Mangosteen is also accompanied by billiard chalks, dropping from the sky in an attempt to crush the player(s). The chalks will try again by jumping in an arc and slamming down on them, the green one jumps the highest, then violet, and the lowest is orange, but this is also easy to avoid. Usually there will only be two different color chalks on screen. In Expert mode, however, all three color chalks can be on screen at the same time.
After enough damage, Mangosteen's body will start melting and a black substance will spill out from his mouth, making him appear to be vomiting.
- The background of the battle with Mangosteen looks very similar to the background that appears when you get farther in the platforming level Funhouse Frazzle.
- Mangosteen is named after a tropical fruit of the same name.
- The attack where he spits out an orb of energy from his mouth is similar to a bomb that the boss Dark Mind can fire from his belly in Phase 1 when Kirby fights him in Kirby and the Amazing Mirror, except there's no catastrophic explosion later.
- Mangosteen's design is a reference to Melon Bread from Gunstar Heroes and other Treasure games, which inspired Cuphead. In fact, analogous to his inspiration, he's also named after a fruit and fires a single ball of energy as his sole direct method of attack, having sensory organs floating and dying animation is puking, just like his inspiration.
- Mangosteen represents billiard games.
- Mangosteen's place is number 8, referring to an 8-ball.
- When Mangosteen fires a colored orb, the sound that is made sounds similar to when two billiard balls collide.
- When Mangosteen is defeated, he spews a black liquid out. This is a reference to Magic 8 Ball toys, which resemble 8-balls and are filled with a blue liquid and a die that can be used to predict the future.
- In the sense that Mangosteen is using it in his death line, the term "hustle" refers to secretly robbing an individual of their money, referring to the fact that many casino games are rigged.
- It can also be referring to the technique of a pool player tricking inexperienced players into losing a game and their money by pretending to be worse than them before the player reveals their actual level of skill. This probably means that Mangosteen thought that Cuphead and Mugman lost to him on purpose.
- Mangosteen's first three words in his death quote refers to types of errors in pool billiards.
- In the unused Simple Mode, he would just look around and never attack, and the billiard chalks would never appear. He only have the default 100 health. In later version like 1.1.3, the Simple Mode differences have been removed and would play like Regular Mode instead.