In Super Mario's Mushroom Kingdom, it is undeniable that the biggest bad guy to threaten Princess Peach and her citizens is the Koopa King, Bowser. However, he is not the only villain threatening the Mushroom Kingdom's security.
Since his first appearance in Luigi's Mansion for the Nintendo GameCube, King Boo has become a recurring boss. Sometimes you play as him, and sometimes he helps you steal coins and stars from your friends. Most of the time, he is here to cause trouble for the Mario brothers and their friends; No matter where the Spectral King appears, you can always be sure he's up to no good.
9 Mario Kart 8 Deluxe
Evil villains go go-karting
Many Mario Kart games let you choose King Boo as your champion of choice. He first debuted Mario Kart as Petty Piranha's partner in Double Dash but then chose to drive alone. Some games retain his main series appearance, while other games let you make Luigi's mansion look more menacing.
This heavy-tier racer may have chosen not to cause too much trouble for Luigi and his friends for now, but there's no telling when the King of Boos will make another go-karting villainous choice.
8 Mario Party Superstars
He will steal for a price
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When Horror Land was originally released in Mario Party 2, the tombstone in the top right corner of the map belonged to Big Boo. When Mario Party Superstars chose to reuse this board, Big Boo was replaced by King Boo.
In this game, King Boo is on your side – for a price. If you meet him with the help of the Skeleton Key, King Boo will offer to steal coins or stars for three times the price of normal Boo. This is because Ghost King takes coins or stars from all your opponents instead of one of your choice. He can be integral in turning the tide in the game if you have enough coins to pay for his services.
6 Super Mario Bros. Wonder
Avoid his operatic chase
King Boo reappears in two stages in Super Mario Bros. Wonder – Light-Switch Mansion and The Final Battle! Bowser's Rage Phase. In these stages, the spectral king follows your favorite hero while singing in an operatic baritone. If he loses his crown, he shrinks to the size of a normal boo.
Like ordinary Boo, King Boo doesn't like to be seen. If you choose to stop running and face him instead, he will cover his face and his singing voice will be distorted. Who knew such a dangerous enemy could be shy?
5 Super Mario Sunshine
Try your luck against the king
Technically, King Boo from Super Mario Sunshine isn't King Boo at all. Bowser Jr. created by E. Gadd. He is Big Boo, created using a magical paintbrush. However, many still consider Sunshine to be one of the King's many appearances.
This Boo appears on the fifth level of Serena Beach, where the boos are terrorizing the Hotel Delfino. If you manage to access him through the basement casino, a boss fight begins where you have to throw spicy pepper into his mouth, which allows you to hurt the ghost. Once defeated, he explodes into paint-like goop, rewarding you with a Shine Sprite for your victory.
4 Mario and Luigi: Paper Jam
Tricks and illusions are his specialties
King Boo returned to Mario & Luigi and Paper Mario Crossover, Mario & Luigi: Paper Jam for no good. When the three split up in the Gloomy Woods, King Boo kidnaps both Mario and Paper Mario, leaving Luigi on his own to search for the two. Luigi finds Mario and the two search for Paper Mario. J
When they think they have found him, King Boo reveals that it was a disguise to make the two brothers look good. During the battle, King Boo captures the real Paper Mario and summons Paper Boo, whom the brothers are ultimately able to rescue. With the help of Paper Mario, the brothers are able to defeat King Boo once again.
3 Luigi's Mansion
King's debut
Luigi's Mansion was King Boo's first true appearance, where he tricked Luigi into thinking he had won a mansion in a sweepstakes that the green-colored brother never actually entered. Thinking that things were suspicious, as he rightly was, Mario goes to the mansion first, only to find it full of ghosts. King Boo captures the older Mario brother and seals him in the figure.
King Boo tries his best to capture Luigi as well, but the recent ghost-spawning brother turns the tide in the battle, even as King Boo gives Bowser a suit to attack. In the end, Luigi emerges victorious and puts King Boo in the picture once again.
2 Luigi's Mansion: Dark Moon
Back for revenge
King Boo reappears at the mansion in Luigi: Dark Moon, eager for revenge. Escaping from his painting, King Boo shatters the dark moon with a magical bolt from his crown, transforming the ghosts of Evershed Valley into chaotic, hostile creatures who serve only him.
At the end of the game, King Boo once again traps Mario in a painting. He plans to do the same to Luigi, E. Gadd, and the rest of their friends but he never gets the chance. Despite his efforts, Luigi collects all six pieces of the Dark Moon and engages King Boo in a final battle, eventually absorbing the ghostly king into Poltergust 5000. Luigi then restores the Dark Moon, returning the ghosts of Evershed Valley to their original friendly but mischievous kingdom.
1 Luigi's Mansion 3
His thirst for revenge grows
King Boo is at his best and scariest in Luigi's Mansion 3, where he uses Helen Gravely to hide Mario, Luigi, Peach, and several Toads in a large resort. The resort is a trap, run by and filled with ghosts loyal to Helen and, by extension, King Boo; He manages to imprint Mario, Peaches and Toads on the pictures before going after Luigi, but the cowardly plumber manages to escape.
Gradually, floor by floor, Luigi defeats the ghostly subjects of Helen Gravely, granting him further access to the hotel, until he finally confronts King Boo. The King of Boos is willing to go so far as to destroy the hotel if it means he will win but, eventually, the King is sucked in by Luigi's poltergast and placed in a containment jar with Helen Gravely. This plan may have failed, but we're excited to see what evil plan King Boo tries next.
