Paper Mario: The Thousand-Year Door

Paper Mario: The Thousand-Year Door is the back-and-forth adventure to collect all of the seven Crystal Stars, enter the Thousand-Year Door, and stop the X-Nauts' plan from unsealing the Shadow Queen to accidentally bring forth eternal darkness.

Prologue: A Rogue's Welcome
Mario receives an invitation from Princess Peach to head to Rogueport to join her in searching for the treasure behind the elusive Thousand-Year Door. Mario arrives but gets jumped into a fight between Lord Crump and Goombella. Toadsworth explains that Peach went missing, which sparks another mystery.

After a talk with Professor Frankly, the trio journey down into Rogueport's sewers to discover the Thousand-Year Door. The map Peach gifted Mario starts to glow and reveals the location of the first of seven Crystal Stars needed to open the Thousand-Year Door: Hooktail Castle.

Chapter 1: Castle and Dragons
Mario and Goombella have arrived at Petal Meadows, but they need to figure out how to reach Hooktail Castle. At Petalburg, they are told that Shhwonk Fortress holds the key to accessing Hooktail Castle. With the two keys to Hooktail Castle, Koops joins the team to prove himself

The climb up Hooktail Castle leads them to the feet-loving Hooktail, holding the first Crystal Star. They defeat her, and out comes Koops's father who had survived for ten years inside her stomach. Mario gets the first Crystal Star.

Meanwhile, it turns out Peach had been kidnapped by the X-Nauts who has taken her to their base.

Also meanwhile, Bowser, hearing about the power of the Crystal Stars and Peach's kidnapping from Kammy Koopa, flies on over to Petalburg.

Chapter 2: The Great Boggly Tree
Mario's trek inside the sewers finds him the location of the next Crystal Star: the Great Tree of the serene Boggly Woods. The tree is unfortunately locked, but there's a secret entrance inside the tree, which needs Madame Flurrie's assistance. But first, Madame Flurrie needs to wear her necklace to ever be seen outside, so Mario, Goombella, and Koops beat up the Shadow Sirens, who stole her necklace in the first place.

With the necklace returned to Madame Flurrie, she's Mario's partner and everyone can enter the Great Tree now. Mario saves all the Puni inside and joins them in a race war against the Jabbi. The team finds the Crystal Star, but Lord Crump snatches it and activates a time bomb inside the Great Tree. After chasing him, he stops the bomb and fights the group in his Magnus von Grapple mech, but that is swiftly destroyed and the second Crystal Star is obtained.

Meanwhile, Peach dances with TEC.

Also meanwhile, Bowser arrives at Petalburg and gets tricked by a life-sized poster of Peach.

Chapter 3: Of Glitz and Glory
The location of the third Crystal Star is in the famous arena of Glitzville. To get there, Mario makes a deal with Rogueport's local mafia boss, Don Pianta, to tickets for a blimp to Glitzville.

Mario, Goombella, Koops, and Madame Flurrie watch a current round of the Glitz Pit and sees Rawk Hawk, current champion of the ring and holding a belt that looks definitely like a Crystal Star. Mario enters as a fighter and fights his way to the top, eventually earning a newly hatched Yoshi to overcome a small hurdle, and beats Rawk Hawk himself.

They do find out that the Crystal Star on his belt is fake beforehand, so the group eventually discovers a massive power-siphoning conspiracy controlled by Grubba. During the matches, Bowser is fought but Mario beats him.

Meanwhile, Peach sneaks around the base and figures out what the X-Nauts are up to: world domination.

Also meanwhile, Bowser enters the Great Tree of Boggly Woods and doesn't achieve anything.

Chapter 4: For Pigs the Bell Tolls
The next Crystal Star is held inside Creepy Steeple near Twilight Town. The town itself is having its own crisis due to the Creepy Steeple bell turning people into pigs. The group enters the Creepy Steeple and beat up Doopliss for the Crystal Star.

Doopliss then swaps places with Mario. Now cursed, Mario befriends one of the Shadow Sirens, Vivian, and beats up Doopliss again to get his original form back. Now Mario truly has the fourth Crystal Star, and the curse on Twilight Town has been lifted.

Meanwhile, TEC plays a quiz against Peach and she learns even more about the X-Nauts plan for world domination.

Also meanwhile, Bowser tries flying to Glitzville but doesn't achieve anything.

Chapter 5: The Key to Pirates
Ms. Mowz needs a badge in Hooktail Castle. Mario gets it and gains Ms. Mowz as a partner.

The fifth Crystal Star is in the Pirate's Grotto in Keelhaul Key. Mario talks with Flavio and Admiral Bobbery and the team sails to Keelhaul Key.

The ship ended up being shipwrecked, but they still manage to reach the spirit of Cortez who gives Mario the Crystal Star. Mario's crew is then under attack by Lord Crump, who had disguised himself as one of Mario's pirate crew. In response, Mario asks Cortez to attack Lord Crump's ship.

Meanwhile, Peach goes invisibly naked to access more information for TEC.

Also meanwhile, Bowser arrives in Twilight Town to achieve nothing and explode the entire town.

Chapter 6: 3 Days of Excess
The sixth Crystal Star is revealed to Mario: the pish-posh Poshley Senctum of Poshley Heights. First they have to get a ticket to the Excess Express, which the group gains after making another deal with the mafia. After solving a train mystery on the Excess Express, Mario, Goombella, Koopa, Madame Flurrie, Mini-Yoshi, Vivian, Admiral Bobbery, and Ms. Mowz make it to Poshley Heights.

The Siren Sisters, fortunately, took an imposter Crystal Star, and Mario grabs the real one.

Meanwhile, Sir Grodus hears of TEC's treason and shuts him down.

Also meanwhile, Bowser achieves nothing.

Chapter 7: Mario Shoots the Moon
Mario's final Crystal Star is currently on the Moon. To reach the Moon, Mario and friends reach Fahr Outpost and get a cannon.

Now on the Moon, Mario lands pretty close to the X-Naut Fortress. Lord Crump fights Mario again using his second version of his Magnus von Grapple. He's defeated and Mario gains the last Crystal Star. TEC tells Mario that Peach is at the Palace of Shadow before shutting down.

Meanwhile, Bowser arrives at Poshley Heights and doesn't achieve anything, but a Paragoomba swoops in to tell him that Mario's achieved all Crystal Stars.

Chapter 8: The Thousand-Year Door
With all the Crystal Stars, Mario is the first to open the gate leading to the Palace of Shadows. They fight Gloomtail and continue further inside. Sir Grodus is beat up before Bowser breaks from the ceiling and also gets beat up.

Grodus heads deeper into the palace and awakens the Shadow Queen, whose awakening brings forth darkness to everything close by. The demon possesses Peach and Mario fights her. With the power of love and friendship and positive thoughts, the Shadow Queen is destroyed.

Dusk arrives, and Mario and Peach say their farewells to his partners and Professor Frankly before leaving by boat.

Back at home, a while later, Mario gets an e-mail from Goombella and gets to read what all his partners are up to. After reading, Peach and Toadsworth visit to tell Mario about a treasure map he had found in the castle's storeroom, and asks him to join them.

Postgame Troubles
Mario returns to Rogueport with everyone waiting for him. A lot of troubles in the Trouble Center are found and fixed throughout the land, such as whacking someone with a hammer to jog their memory.

With the Pit of 100 Trials being accessible, Mario goes down and defeats everyone as he and his team goes further and further down. At the very bottom, the undead Bonetail awaits and is defeated. The pit is revisited two times to solve two troubles at the Trouble Center.

Timeline

 * The crows in Twilight Town reference Luigi's Mansion through their dialogue, placing this game after that title.
 * This game features the pre-Superstar Saga Bowser's Castle design.
 * This game is likely the first appearance of Peach's modern dress chronologically, as she’s in her classic dress for the majority of the game but the dress resembles her modern one while she is possessed by the Shadow Queen.
 * This game is likely Toadette's first chronological appearance as when Mario first meets her here she introduces herself to him. The last time Mario meets her she believes it is the last time she’ll ever get to see Mario and is very sad about it. She is also wearing an orange dress in this game, as opposed to the pink dress she is seen to be wearing in every other title.