Mario and Luigi: Revenge of the X-Nauts is a game for the DS. It involves elements from Paper Mario: The Thousand Year Door and Super Mario Galaxy.
- Mario - The fearless warrior of the Mushroom Kingdom, he works together with the others to restore the Star Comet.
- Luigi - A comical warrior who is cowardly, He trys to help a lot, which leads to mishaps.
- Geno - A warrior from the stars, is dead serious with his work.
- Bowser - A koopa who decides to help Mario because he will restore riches.
- Princess Peach - The beautiful princess of the Mushroom Kingdom, is kidnapped by Grodus and his band of X-Nauts.
- Toads - Princess Peach's faithful servants, often run shops.
- Popple - A beanish thief who is vacationing in the Mushroom Kingdom, He tells secrets to the gang.
- Yoshi - A dinosaur from Yoshi's Island, only appears in that perticular stage.
- Koopalings - Bowser's eight children. They appear to help their father.
- Koopa Troop - Bowser's army. Appear in various areas, most notably Bowser Castle.
- Piantas and Nokis - Two peaceful species from Isle Delfino. Appear in tropical stages.
- Mallow - The prince of Nimbus Land returns as an ally.
- Toadsworth - Peach's steward, only appears in Toad Town.
- Princess Daisy - The princess of Sarassaland, she runs the mushroom kingdom while Peach is kidnapped.
- Flavio - A snobby merchant from Rogueport, never leaves his house now in fear that Zess T. will hit him with the frying pan again.
- Cortez - The undead pirate king, sails with Bobbery, is seen at Keelhaul Key.
- Bobbery - A bob-omb and an ally of Mario, sails with Cortez.
- Jolene, Rawk Hawk and the Glitz Pit gang - Are not fought, but appear as allies through Glitzville
- Ms. Mowz - A mowz who is a badge thief, appears to give badges.
- Prince Peasley - The prince of the Beanbean Kingdom.
- Queen Bean -The Queen of the Beanbean kingdom.
- Zess T. - A toad chef, plays the same role as she did in PM2.
Enemies and Bosses
- Goombas - Tanoomba, Terekuribo
- Koopas - Koopleon, Koopie, Heavy Troopa.
- Shy Guy - Boom Guy, Boo Guy, Fat Guy.
- Snifits - Flifit, Flofit
- Cheep Cheeps - Cheep X
- Chain Chomps - Chomp X, Fawflomp
- Beanie - Jelly.
- Bumpty - Blazing Bumpty
- Spike - Acid Spike
- Boo - Bomb Boo, Booooooo
- Piranha Plant - Egg Piranha, Speedy Piranha
- Misc. - Swooper, Pendrill, Air Cannon, Blooper, Clubba, Cosmic Clones, Magikoopa.
- Grodus - Infinite - Star Hill
- Punchinello - 150 - Naut Forest
- Magnus III - 200 - X Factory
- Koopa Bros. - 50 (Each) - Bowser Castle
- Hooktail, Gloomtail and Bonetail - 100 (Each) - Castle Vault
- Midbus (Easter Egg) - 200 - Basement.
- Gooper Blooper - 300 - Oho Ocean
- Lord Crump - 400 - Oho Beach
- Wiggler - 450 - Bean Forest
- Bouldergeist - 500 - Boulder Mountain
- Mouser - 550 - Koopa Cruiser
- King Boo - 650 - Koopa Cruiser Engine Room
- X-Naut Storm - 700 - Koopa Cruiser Balcony
- Bowyer - 800 - Koopa Cruiser Storage
- King Bill - 900 - Monty Mountain
- Undead Grubba - 950 - Glitz Pit
- Huff 'N Puff - 1000 - Cloudy Climb
- Dark Bowser - 1200 - Bowser Starship
- King Puffer - 1400 - Oho Ocean Revisted (Optional)
- Bugaboom - 1600 - Naut Forest Revisted (Optional)
- Grodus - 1800 (But doesn't officilly die) - X Naut Space Station
- Axem Rangers 2.0 - 500 (Each) - Bowser Keep
- Giga Lakitu - 3000 - Yoshi's Island
- The Underchomp - 4000 - X-Naut Fortress
- Grodus - 5000 - X-Naut Fortress
- Smithy - 10000 - X Naut Fortress (Final Boss)