“Get it together, Private Goomp! Let's scout this area, at least.”
—Sergeant Guy, Mario & Luigi: Bowser's Inside Story
Sergeant Guy is a Green Shy Guy that carries a silver pipe and Magikoopa's wand on his back. He is a minion of Bowser in Mario & Luigi: Bowser's Inside Story.
 Mario & Luigi: Bowser's Inside Story
He is first seen with Corporal Paraplonk and Private Goomp attempting to take Bowser's Castle back from Fawful with a Banzai Bill Blaster. However, the minions have no ammo and Bowser is forced to go inside and get some ammo. Once Bowser obtains the Banzai Bill, the three minions fire it into the castle.
When Bowser turns into Giant Bowser, he applauds when Bowser inflicts damage to Bowser's Castle as Corporal Paraplonk teaches Bowser how to battle.
Later on, in the Treasure Chamber in Bowser's Castle, Sergeant Guy and his companions watch Bowser defeat the Fawful Express and once Bowser opens the safe, Sergeant Guy and the other minions push Bowser into the safe, stating that Fawful bribed them with rations.
Sergeant Guy was seen after the closing credits, where he and the other minions apologize for their treason, and ask Bowser if they could rejoin the Koopa Troop. Bowser forgives them on one condition: they have to help with castle repairs.
 Mario & Luigi: Dream Team
In Mario & Luigi: Dream Team it is revealed that Sergeant Guy was promoted along with his associates to Bowser's Royal Guard. He has a flag with a Bowser emblem on it. He travels with Bowser to Pi'illo Island to find Princess Peach. Sergeant Guy also helps Kamek disguise as Princess Peach forming a lower section of the disguise. It is also shown that he and his associates dream of bossing around Kamek & Bowser one day. The trio are also fought in a boss battle as the Elite Trio.
After being defeated, Kamek demotes them to janitors and sends them back to the castle. After Bowser was defeated, he, Kamek, Private Goomp, Sergeant Guy and Corporal Paraplonk decided to retreat. Although Bowser was really mad that his plan had failed and that it was Antasma's fault, he told his three minions that they did pretty well by their usual standards, much to their joy.
 Sergeant Guy X
Sergeant Guy also appears in the Battle Ring, as Sergeant Guy X. He fights alongside his comrades as the group now called Elite Trio X. They are fought in the Normal Class 6 battle. Unlike most Battle Ring X bosses, but like his allies' X versions, there is no change in appearance between versions. He has the boosted stats all of Battle Ring's X bosses have.
 Names in Other Languages
|Pun on heifer.
||Sargento Shy Guy
||Sergeant Shy Guy
||Sergeant Guydo(Pun on "Shy Guy" and "Guido", an Italian name rarely used in Spain)
||Pun on "Maskass" (Shy Guy's French name) and the childish suffix "-ou".
||Portmanteau of "Shy Guy" and the male name "Guido".
||"Guy Guy". Taken together with Private Goomp and Corporal Paraplonk's names, their names are derived from the Italian expression "Tizio, Caio and Sempronio", meaning "three random guys".
- His Italian name, along to Private Goomp and Corporal Paraplonk's ones, references the Italian terminology "Tizio, Caio and Sempronio", meaning "three random guys".
- Sergeant Guy shares the rank and coloration of Keroro from the anime Sgt. Frog.
- In Mario & Luigi: Bowser's Inside Story, Sergeant Guy wore brown shoes; in Mario & Luigi: Dream Team, they are now blue.