| Paper Mario: The Thousand-Year Door Enemy
| Max HP
|| The Great Tree|
|| A foot soldier that uses potions and attacks by ramming. This X-Naut is the lowest of Grodus's underlings.
|| Dizzy Dial, Stopwatch, Fire Flower, Super Shroom
|| Ground Pound (3), Tackle (3), Potion (Huge)
|That's an X-Naut. Says here it's classified as an `enemy combatant'. This description stinks... You think it means they're just low-level foot soldiers? Max HP is 4, Attack is 3 and Defense is 0. They drink these potions that make them all big and burly and they attack! One's easy, but if there's two or more, better watch out! Use special moves and items!
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“You rang, dude? I mean, sir? You rang, Sir Grodus, dude? Grodus? Sir Grodus, sir?”
—X-Naut, Paper Mario: The Thousand-Year Door
The X-Nauts are soldiers that work for Grodus and Lord Crump of the Secret Society of the X-Nauts; they all appear in Paper Mario: The Thousand-Year Door. They are short and individually weak, but rush to defend their leader, Lord Crump, if he is threatened. It is unknown what is behind their uniform, as they don't show their true appearance, just like a Shy Guy.
Several X-Nauts were encountered in the Great Tree as they and Crump searched for the Emerald Star. The surviving X-Nauts were forced to retreat when Crump was defeated. During the boss battle with Lord Crump in Keelhaul Key, some X-Nauts helped him. Also, some were encountered in the X-Naut Fortress, including X-Naut PhD's and Elite X-Nauts. At least four X-Nauts aside from Crump survived, and are shown in the ending sequence: A regular X-Naut soldier, an X-Naut PhD, and two Elite X-Nauts.
A large army of X-Nauts (exceeding any count of X-Nauts seen in the Great Tree or X-Naut Fortress) is often summoned by Lord Crump. When Mario defeated Crump the first time, he summoned the X-Nauts (which included a regular X-Naut named Johnson) to attack Mario, but they accidentally attacked Crump instead while Mario and Goombella escaped. Later, on Keelhaul Key, Crump brought the army of X-Nauts with him on a battleship to attack Mario and take the Sapphire Star back from him. They fought against the Toads and Cortez's Embers, and eventually Crump called them in to assist him in the fight against Mario, but when Crump was defeated, he and the army retreated. Shortly afterward, when Crump encountered Bowser and Kammy Koopa in Twilight Town, Crump summoned the army of X-Nauts again. Bowser and Kammy retaliated by summoning various members of the Koopa Troop (Hammer Bros., Koopatrols, and Magikoopas). Crump threw a Superbombomb at them, but as it was broken it didn't work. Bowser set it off with his fiery breath, destroying both armies (though Bowser, Kammy, and Crump survived).
In recent years, X-Nauts have (according to Super Paper Mario) been featured in two sci-fi TV shows: Starship X-Naut and The Grodus Chronicles (the latter of which is only known to have featured one X-Naut whose lover had dumped him). There have been many seasons of Starship X-Naut, and the show is a favorite of geeks such as Francis. Apparently, he favors people who would dump somebody over a conversation about the propulsion system of the X-Nauts' spaceship on the show. An X-Naut made a cameo appearance on the Nintendo Monopoly board.
 Varieties of X-Nauts
- X-Naut troopers are the lesser X-Nauts, also the weakest. These types of X-Nauts are field troops and the lowest of Grodus' underlings. When led by high-ranking commanders, such as Lord Crump, they can use more attacks.
- Elite X-Nauts
- X-Naut PhDs
 Notable X-Nauts
 X-Naut Platoon Stats
- HP: 6 (for the first round), 10 (second round)
- Attack: 5 (Decreases as HP is lost)
- Defense: 0
- Location: Keelhaul Key
- Tattle: That's an X-Naut platoon. Crump commands them all. Where'd they come from? Their Max HP depends on their condition, but Attack is 5 and Defense is 0. They're gonna come at us with coordinated group maneuvers, I'm sure. ...But they're pretty wimpy, so we should be able to handle it, don'tcha think?
- Attacks: Team Body Slam (5), Individual Fall (1x5), Ceiling Forks (4, both characters), Combined Roll (5, both characters)
 Names in Other Languages
||Mega (or Big) X
||Portmanteau of "cruxi-" (a prefix referring to a cross) and "troufion" (low-ranked soldier)
||From Latin "crux" meaning cross, "-ionen" is a standard suffix like the English "-ions"
- The original name for the X-Naut in the demo version of The Thousand-Year Door was "Boomer Ganger".
- Due to the lack of voice acting in Paper Mario: The Thousand-Year Door, the actual pronunciation of "X-Naut" is unknown. It's possible that it's pronounced "ex", like the letter "X", or it could be pronounced "cross", like the X-Yuxes. Although the word "an" was applied to the X-Nauts, it should also be noticed that it was incorrectly applied to the X-Yuxes in Goombella's Tattle, as well (unless she pronounced it "Ex-Yux" first, before revealing its actual pronunciation).
- In Super Paper Mario, there is a Sammer Guy by the name of Laughing X-Naut.
- ^ http://www.youtube.com/watch?v=VDMEQrZ92IA, around 25:35