"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.
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 its 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.
After enough damage, his body will start melting and a black substance will spill out from his mouth, making him appear to be vomiting.
Mangosteen seems to be quick to jump to conclusions, possibly sometimes not realizing that said conclusions are false, considering that he accuses Cuphead and Mugman of "hustling" 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 defeated.
- Mangosteen is named after a tropical fruit of the same name.
- 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.
- His design also looks like Tobor from the Adventures of Sharkboy and Lavagirl.
- Mangosteen's eyes and mouth may also be inspired by N. Boss from ClayFighter.
- 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.
- When Mangosteen moves to launch his color spectrum orbs at Cuphead and Mugman, this might be a reference to the Dark Mind battle from Kirby and the Amazing Mirror when Dark Mind attempts to destroy the four Kirbies with a bomb of a similar fashion.
- In the sense that Mangosteen is using it, 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.