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Species name: Boo (Teresa in Japanese, a pun on “tereru” meaning “to be shy”) First Appearance: Super Mario Bros. 3 (NES, 1988, as “Boo Diddly”) Home: Various haunted manors and ghost-themed locations across the Mushroom Kingdom Voiced by: Wordless giggle and ghost-laugh vocalizations across all appearances Notable individual Boos: King Boo (their monarch), Lady Bow (Paper Mario, 2000), Bootler (her butler), Big Boo, Boolossus (Luigi’s Mansion), Peeka and Lahla (TTYD) |
General profile
The Boo is one of the most-distinctive enemy species in the Mario series, defined by their unique gameplay mechanic of being unable to attack Mario while he is looking at them. Introduced as “Boo Diddly” in Super Mario Bros. 3 (NES, 1988), Boos are small, round, ghost-shaped creatures with sharp pointed teeth, a long protruding tongue, two tiny arms, and an almost-permanent expression that flips between cheerful and menacing depending on whether they are being observed. Their visual silhouette, a white round ghost-orb shape with a face, has remained essentially unchanged across the species’ 35-year history and has become the immediately-recognisable shorthand for “Mario series ghost enemy.”
The Boo’s defining gameplay mechanic is their “shy-when-watched” behaviour. When Mario faces a Boo directly, the Boo covers its face with its arms and stops moving, becoming temporarily harmless. When Mario turns his back, the Boo uncovers its face, reveals its sharp teeth and protruding tongue, and pursues Mario with surprising speed. This dual-state gameplay mechanic, introduced in Super Mario Bros. 3 (1988), has been preserved unchanged across every mainline Mario series platformer that features the species. The mechanic creates a unique gameplay tension that Mario series fans have praised as one of the most thematically-clever enemy designs in the franchise.
The Boo species’ broader Mario series role expanded significantly with the introduction of King Boo, their imperious monarch, in Luigi’s Mansion (GameCube, 2001). The Luigi’s Mansion sub-series established the species’ formal political hierarchy: King Boo as the species’ royal leader, the Boos as his subjects, and Luigi as their species’ primary nemesis. The species has been featured prominently in every Luigi’s Mansion entry (2001, 2013, 2019), in Super Mario 64‘s Big Boo’s Haunt level (1996), in Super Mario Sunshine‘s haunted hotel chapter (2002), in the Paper Mario series (where Lady Bow is one of the most-loved Paper Mario party members), and as recurring playable characters in Mario Kart, Mario Party, and Mario sports spin-offs.
Quotes
Enemies
The Boo species’ primary enemies are Mario, Luigi (their species-monarch King Boo’s personal nemesis), and the wider Mushroom Kingdom heroic cast. Their species-leadership under King Boo aligns them with Bowser’s broader villain coalition in spin-off contexts, making them opposed by default to essentially every protagonist character in the Mario series. The species’ “shy-when-watched” mechanic gives them a unique combat dynamic, the only way to defeat them in standard 2D Mario platformers is via fire flowers, star power-ups, or specific level-ending mechanisms, jumping on them does not work due to their incorporeal ghost-nature.
Friends
Boos’ loyalties vary by individual. The mainstream Boo species serves under King Boo’s royal authority and aligns with Bowser’s broader villain coalition. However, several notable individual Boos have allied with Mario or with neutral parties. Lady Bow (the noble Boo princess from the original Paper Mario, 2000) and her butler Bootler are the most-prominent good-aligned Boos, with Lady Bow joining Mario’s party as a major late-game ally. Peeka and Lahla, the Boo characters in Paper Mario: The Thousand-Year Door (2004), are similarly good-aligned exceptions. The Boo species’ political-hierarchy nature means that individual exceptions are possible but rare.
Appearances
Super Mario Bros. 3 (NES, 1988) as “Boo Diddly”
The Boo species debuted in Super Mario Bros. 3 for the Nintendo Entertainment System (October 1988, Japan; February 1990, North America) as “Boo Diddly,” the species’ original Western name. The character was designed by Nintendo R&D4 as one of the original SMB3 enemy roster. The shy-when-watched mechanic that defines the species was introduced in this game and has been preserved unchanged across every subsequent mainline Mario series platformer.
Super Mario 64 (1996) and Big Boo’s Haunt
Super Mario 64 (1996) introduced the Big Boo’s Haunt level, a Boo-themed haunted mansion that gave the species its first significant 3D environment. The level features standard Boos, larger “Big Boo” variants, and the boss-tier King Boo (or his predecessor, “Big Boo” in this entry). The 64-era Boo design preserves the species’ iconic silhouette while adapting it to the new polygonal graphics technology.
Luigi’s Mansion (GameCube, 2001)
Luigi’s Mansion (GameCube, 2001) established the Boo species’ modern hierarchical structure, with King Boo as their formal royal monarch and the Boos as his subjects. The game features over 50 unique Boo enemy characters that Luigi must capture using the Poltergust vacuum cleaner across the haunted mansion campaign. Each captured Boo has a unique name and individual personality, an unusual character-design depth for what is essentially rank-and-file species fodder.
Super Mario Sunshine (GameCube, 2002)
Super Mario Sunshine (2002) featured Boos prominently in the Hotel Delfino haunted-hotel chapter of the Pinna Park region. The game’s Boo design gave the species more detailed shell texturing, anatomical refinement, and animation polish than previous-generation 3D appearances. The Sunshine-era Boo design influenced subsequent 3D Mario series Boo character models.
Paper Mario series (2000-present)
The Paper Mario series has featured Boos prominently across multiple entries. The original Paper Mario (Nintendo 64, 2000) introduced Lady Bow, the noble Boo princess who serves as one of Mario’s major party members in the late game. Paper Mario: The Thousand-Year Door (GameCube, 2004) features Peeka and Lahla, two good-aligned Boo characters in the Glitzville and Twilight Town regions. The 2024 Switch remake of TTYD reintroduced these characters to a new generation of fans.
Mario Kart series (2003-present)
Boos have been recurring playable racers in the Mario Kart series since Mario Kart 64 (1996, where they appeared as the Boo item rather than as a playable character). Mario Kart: Double Dash!! (GameCube, 2003) introduced Boo as an unlockable playable character, and subsequent entries have featured Boos as default or unlockable racers. Mario Kart Tour (mobile, 2019-2025) and Mario Kart World (Switch 2, 2025) both feature Boo as a standard playable racer.
Super Mario Bros. Wonder (Switch, 2023)
Boos returned in Super Mario Bros. Wonder for Switch (October 2023) with subtle visual refinements. The species’ role as a recurring rank-and-file ghost enemy was preserved, with several Wonder Effect transformations giving standard Boos altered behaviour patterns. The game features various Boo sub-types including standard Boos, larger Big Boos, and the recurring King Boo as the boss of the “King Boo’s Maze” level.
Trivia & Official Sources
- The Boo species was designed by Nintendo R&D4 for Super Mario Bros. 3 (1988). The species’ “shy-when-watched” gameplay mechanic was inspired by the work’s lead character designer Takashi Tezuka’s wife, who according to Mario series lore would only look at her husband when he was not watching her, a deliberately personal creative reference that has become canonical in supplementary Mario series materials.
- The Japanese name Teresa is a feminine name combined with a pun on “tereru” (to be shy or embarrassed). The Western name “Boo” derives from the traditional ghost-vocalization of “boo!” and was created for the 1988 SMB3 localisation by Nintendo of America.
- The Boo’s “shy-when-watched” gameplay mechanic, where the species is harmless when Mario looks at it but aggressive when his back is turned, has been preserved unchanged across every mainline Mario series platformer since 1988. The mechanic is one of the most-iconic gameplay designs in the franchise.
- The Pix’n Love Encyclopedia Super Mario Bros. (2018) describes Boos as “the ghost species of the Mushroom Kingdom, subjects of King Boo, distinguished by their shy-when-watched behaviour.”
- King Boo, the Boo species’ royal monarch, was introduced in Luigi’s Mansion (2001). The Luigi’s Mansion sub-series established the species’ formal political hierarchy that has been preserved across all subsequent Boo appearances.
- Lady Bow, the noble Boo princess from the original Paper Mario (Nintendo 64, 2000), is the most-prominent good-aligned individual Boo in the Mario series. She serves as one of Mario’s major party members in the late game, an unusual role for a typically-villainous species.
- Boo variants in the Mario series include Big Boo (larger), Bigger Boo (even larger), Boolossus (an enormous fused Boo from Luigi’s Mansion), Peekaboo (Mario Tennis variants), Stretch Boo (elongated), and the King Boo himself (the royal monarch). Each variant has distinctive combat behaviours.
- The Boo species’ “Bow” sub-name has been used in several Mario series entries to refer to the species’ royal-noble individuals. Lady Bow in Paper Mario uses this convention, distinguishing her from rank-and-file Boos.
- Boo amiibo figures have not been released as standalone products. The species has been featured in background art of various Mario series amiibo line promotional materials.
- The species’ “Boo” Western name has been preserved unchanged across all localisations and re-releases since 1988. Some Mario series materials have used the alternative “Ghost” descriptor, but this has not become canonical.
- Big Boo’s Haunt in Super Mario 64 (1996) was the species’ first significant 3D environment. The level features a Boo-themed haunted mansion that established many of the modern haunted-house conventions of the Mario series.
- The Luigi’s Mansion series (2001, 2013, 2019) features over 100 unique individually-named Boo characters across its three games. Each captured Boo has a distinct personality, name, and aesthetic, an unusual character-design depth for what is essentially rank-and-file species fodder.
- The Boo’s pink-and-yellow tongue protruding from its mouth has been canonised as the species’ signature visual feature alongside the round white body. The tongue is shown sticking out during the Boo’s aggressive state when Mario’s back is turned.
- The Boo has appeared as a playable character or Mii Fighter costume in various Super Smash Bros. entries. The species has been included as a Spirit in Super Smash Bros. Ultimate (2018) with combat modifiers reflecting the shy-when-watched mechanic.
- The Boo has been confirmed by Illumination to appear in The Super Mario Galaxy Movie (April 2026) alongside King Boo. The species’ film appearance is set to feature several haunted-house themed action sequences that pay homage to the iconic Mario series Boo enemy designs.
- Boos have appeared in over 40 Mario series games across the species’ nearly 40-year history. The species’ “shy-when-watched” mechanic and distinctive ghost-aesthetic have made it one of the most-recognised Mario series enemy types.