Back at Peach's Castle, King Boo, Booario, and Booigi have just reappeared from dropping Mario and Luigi into Barrel Volcano. When they arrive back at the castle, the three of them see Princess Boo is surrounded by Toads.
Toad: What happened to you, Peach?
Princess Boo: Why do you keep calling me that?
Another Toad: Because that's your name.
Then a blue fireball is sent above the Toads’ heads. They turn around and see King Boo.
King Boo: I suggest you leave her alone before me and the Boo Bros. do something to you!
The Toads scream and run away. King Boo then approaches Princess Boo.
King Boo: Ah, my sweet princess. I have exterminated those Mario Bros. for you.
Princess Boo: Thank you, King Boo.
King Boo: Now, since we are the rulers of this kingdom, we must make some rules.
Princess Boo: Like what?
King Boo: Well for starters, only Boos, ghost-like enemies, and Dry Bones are allowed to live in this Kingdom. Also, the new name of this kingdom is now the Mushboo Kingdom.
Princess Boo: But how are we going to make the residents leave?
King Boo: Leave that to me.
He turns to Booario and Booigi.
King Boo: You two, gather all the Boos, ghost-like enemies, and Dry Bones back at the mansion. We are going to scare the residents away!
Booario and Booigi: Yes sir!
They disappear back to the mansion and within minutes, they return with all the residents of the mansion.
King Boo: My fellow minions, no longer are we going to live in the mansion on the outskirts of Boo Woods. We will be living here, in the newly named Mushboo Kingdom! And some of you will be living in the newly named Boo Town. But before we do that, we must get all the Toads out of here! So I need Booario, Booigi, and Boolossus to scare all the guards and other Toads in the castle. The rest of you will scare every Toad in town. Now get to it!
The Boos rush off to scare the town. Eventually the Toads gather their things and run out of town and head for places like Koopa Village, Dry Dry Outpost, and Shiver City. Some even take a boat ride to Rougeport and live in Petalburg, Twilight Town, and Poshley Heights. Eventually the Boos report back to King Boo.
Boo: Sir, we have scared away the town.
Booigi: We have also cleared the castle.
King Boo: Excellent. Now, time to perform the spell.
King Boo floats up through the ceiling and floats into the sky. His stubs then let off magic dust. He then spreads a wave of magic over the kingdom and now, the houses are shaped like Boos instead of Mushrooms. He also give the castle a makeover by making it look like his old mansion, only bigger, and the inside still looks like Peach's Castle, only scarier. He floats back down and tells the residents of Boo Town what he has done.
King Boo: Now, before you go to town and claim your homes, I would like to introduce you to the new royal member of the Boo army. Meet, Princess Boo.
Princess Boo floats up next to King Boo, and every Boo claps.
King Boo: All right, go and claim your homes. But, I would like Boolossus, a couple Ghoul Guys, Boo Guys, Fishin' Lakitu ghosts, Spear Guy ghosts, Boos, and Dry Bones to stay within the castle grounds so you can chase off any intruders. The rest of you can go on and get your homes.
The Boos leave except a select few ghosts, Boos, and Dry Bones. Booario and Booigi also stay.
Booario: What about us?
King Boo: You can claim Mario and Luigi's old home.
Boo Bros: All right!
They rush off to Mario and Luigi's house and redecorate it. King Boo then laughs.
King Boo: Hehehehehehehe! This is perfect. Mario and Luigi are gone, and I have a new princess by my side. Nothing can go wrong!
Boolossus: Except one thing.
King Boo: What?
Boolossus: Well, it’s big, and breathes fire.
King Boo: What are you talking about?
Just on cue, a Koopa bursts through the window in a Clown Copter. He jumps out and approaches King Boo.
??????: I've come to kidnap the princess!
King Boo: Oh yeah. Him.
***
Deep within Barrel Volcano, two figures are seen motionless. One is wearing blue overalls and a red shirt, has a mustache, and wears a red hat with an M on it. The other also has blue overalls and a mustache, only he wears a green shirt and a green hat with a green L. The red figure starts waking up.
?????: Oh, what happened? Peach invited us over and then King Boo came, turned Peach into a Boo, and beat us in a battle... ! King Boo.
The figure looks at the green figure and tries to wake him up.
?????: Luigi. Luigi, get up. LUIGI!
The green figure gets up and looks around and sees the red figure.
Luigi: Mario, don't do that!
Mario: Sorry.
Luigi: Man, I don't think I have ever been beaten that badly before.
Mario: Yeah. We have to get back to the Castle and save Peach.
Luigi: First, we have to figure out where we are in the volcano.
Mario looks around and mostly sees walls, with just one open way.
Mario: Well, this must be the first room of the volcano. The only thing is that there used to be a spring here that would shoot you out. But I don't see it. I also can't shake the feeling that there is an old adversary in the volcano. I guess we will find out.
Mario and Luigi get up and start heading through the volcano, trying to withstand the heat.
Mario: If I remember right, Hinopio's shop is right up those stairs.
Luigi: Who's that?
Mario: He helped me by giving me fire armor and items, and letting me and the others rest.
The Mario Bros. jump up the stairs, but run into two Armored Ants, two Vomers (they look like Dry Bones, only located in Barrel Volcano), and a Stompet.
Mario: Uh oh.
The Armored Ants charge at Mario and Luigi and try slashing them with their swords. The Vomers starts chucking bones at the Bros. They jump over the ants and avoid the bones, but land in front of Stumpet. He starts shooting out Magnuses, which start charging at the Bros. They jump on them, but the Magnuses felt nothing.
Mario: This would be easier if I had my hammer!
Just then Mario is hit in the back of the head with a bone, and is knocked out.
Luigi: MARIO!
Luigi is then hit in the back of the head with a bone as well. The Armored Ants, Vomers, and Magnus' approach the unconscious Bros. Then, a figure appears and launches itself into the Vomers, destroying them. The figure then takes a bone from each Vomer and starts hitting the ants and Magnuses with them. They eventually run away, but the figure grabs one ant and takes his sword. The figure then turns to Stumpet and starts slashing him with the sword. He eventually falls apart. The figure picks up Mario and Luigi and takes them through a doorway.
***
??????: All right, where is she?
The Koopa then notices King Boo.
??????: King Boo? What in the name of Morton are you doing here?
King Boo: Taking over the Mushroom Kingdom! Something you couldn't do!
Princess Boo: King Boo, who is that?
King Boo: He's some stupid Koopa who always tries to steal the princess of this Kingdom. That is, until I stepped in!
??????: STUPID?! I am NOT stupid! Now, I don't have time for you! I need to find the princess before the Mario Bros. come.
King Boo: ... Boolossus, take Princess Boo to her room. It's going to get ugly.
Boolossus: Understood.
Boolossus takes Princess Boo and they both teleport. King Boo approaches the Koopa.
King Boo: Look, I know you are usually the last to hear things, so I might as well tell you. I have taken over the Mushroom Kingdom and renamed it the Mushboo Kingdom. There is nothing but Boos, ghost-like enemies, and Dry Bones living in the kingdom. I have exterminated the Mario Bros, and, you're going to LOVE this. I have turned Peach into a Boo.
??????: ... GRRRRRRRRRRRRRRRR! HALF OF WHAT YOU SAID WAS GOING TO BE MY PLAN! KING BOO, YOU HAVE CROSSED THE LINE!
The Koopa breathes fire at him, but King Boo turns invisible.
King Boo: Calm down, Bowser. You know you couldn't have pulled off a plan this brilliant.
Bowser: I'll make you eat those words!
BOSS: Bowser
Bowser charges toward King Boo and tries to slash him. But King Boo is too quick and avoids it. He then breathes a stream of blue fire. Bowser counterattacks by breathing his own stream of fire. The two streams collide and explode. Smoke then engulfs the entire room. King Boo takes this chance to sneak-attack Bowser. He turns invisible and stays like that until the smoke clears. Bowser looks around and tries to find him, but is having no luck. He is then licked in the face by a blue tongue. Bowser falls on his knees and can't get up.
Bowser: Wh...wh...what did you do to me?!
King Boo: Bwhahahahahahaha! My licks have the ability to paralyze my enemies. Oh, and I also picked up a new trick. Get ready, Bowser!
King Boo opens his mouth and forms a bright blue ball. Bowser looks up and notices it.
Bowser: What are you doing?
King Boo: Firing the ICE BEAM!
King Boo fires a beam of ice at Bowser, who takes serious damage and becomes frozen. King Boo laughs.
King Boo: Bwahahahahahahahahaha! Take that, Bowser! Now to dispose of this ice block. I hope you like being with the Mario Bros, because I am dropping you off at the same place I exterminated the Mario Bros!
King Boo uses his psychic powers to levitate the block of ice Bowser is trapped in and they both teleport away.
***
??????: Hey, Mario. Wake up.
Mario is seen sitting on a long, wooden box. He starts waking up, but his vision is blurry. He can't make out what he is seeing, but he can detect a yellow puffball wearing blue and white-striped pants. Next to him is a Toad with a tattoo.
Mario: Uh... Ma...Mallow?
Mallow: Mario, you’re waking up. Hey, Hinopio, he's waking up!
The tattooed Toad, Hinopio, walks over.
Hinopio: Oh, thank goodness.
Mario: Mallow, what's going on?
Mallow: Oh, well, Hinopio found you unconscious outside his shop, so he drove away the enemies by using their own weapons against them.
Mario: But why are you here?
Mallow: Hinopio invited me over, and I didn't want to turn him down. So I came over and we were having a really good time.
Mario: Well, that’s great... Wait, where's Luigi?
Hinopio: Don't worry, he's sleeping on the box next to you.
Mario turns and sees Luigi.
Mario: Oh...
Mallow: So tell us, what are you doing here?
Mario starts telling them the story of how King Boo turned Peach into a Boo and how he knocked them out and threw them into the volcano.
Mario: The only thing I don't get is how he did it. All I remember is that he gave her a white pendent... ! The pendent! That’s how she became a Boo! Once she put it on, it must've activated. Once Luigi wakes up, we have to stop King Boo.
Mallow: I don't understand how you lost, though. You're THE Mario.
Mario: I didn’t have any of my items. No hammer, no Lazy Shell, nothing!
Mallow: ... You said you have to save Peach, right?
Mario: Yeah.
Mallow: Well, make room, because I'm going to help.
Mario: Really?
Mallow: Yeah, I had fun traveling with you when we were searching for the Seven Stars. Ever since then, I have always wanted to go on another adventure with you.
Mario: Thanks. Welcome to the team.
Mallow: All right!
He turns to Hinopio.
Mallow: Could you tell my parents that I'll be traveling with Mario?
Hinopio: Of course, my boy.
Then, Luigi starts waking up.
Luigi: Mamamia. What happened?
Mario: Hey-a Luigi, I found one of my old friends.
Luigi looks and sees Mallow.
Luigi: And you are?
Mallow: Oh, my name's Mallow. I am the Prince of Nimbus Land.
Luigi: Wow, a prince. That’s pretty cool.
Mario: He's going to help us on our journey.
Luigi: Great.
Mallow: Well, let’s go.
They head off, but before they go, Mario realizes something.
Mario: Wait. We can't go yet.
Luigi: Why?
Mario: Like I said before, I can't shake the feeling that there is an old adversary of mine here. So we need some help, like items and armor.
He turns to Hinopio.
Hinopio: You're just in luck. I got a shipment not too long ago, and I now sell attack items.
Mario: Great. Do you sell hammers?
Hinopio: Yup.
Mario: All right! Okay, I'll take two hammers, two fire shirts, and a pair of fire pants.
Hinopio: Coming right up.
Hinopio hands Mario two shiny metal hammers, two red shirts, and a pair of red pants.
Mario: Now, how much is this going to cost?
Hinopio: Oh, don't worry, my friend, this shall be free.
Mario: Really, why?
Hinopio: Like you said before, you have no weapons. You're going to need all the help you can get.
Mario: Thanks.
Mario takes a shirt and a hammer. He tosses the pants to Mallow and the other shirt and hammer to Luigi. They put the clothes on over their old shirts and pants and head off to the end of Barrel Volcano, where they are in for an unpleasant surprise.
Mario, Luigi, and Mallow are seen in a room filled with nothing but lava. Then, six Podoboos appear and start spinning around each other. They then gather in close and fuse. They have turned into the Czar Dragon!
Czar Dragon: GWHOOOOOOOOOOOOO!
Mario: I knew it! I knew he was going to be here!
Luigi: Wh...who is that?
Mallow: It's the Czar Dragon!
Mario: I thought we took care of you a while back.
Czar Dragon: GWHOOOOOOOOOOOOOO!
Mario: Oh yeah, you can't talk.
Mallow: Well, the only way to get out of this volcano is to beat him in battle!
BOSS BATTLE PART 1: Czar Dragon
Czar starts by launching fireballs at our heroes. They jump to avoid the shots. Mario charges in and smashes him with his new hammer. Czar roars in pain and uses the magic attack boulder. He summons large boulders and sends them Mario's way. Just has he is about to get hit, Mallow jumps in and uses his Sonic Symbols. He sends a shockwave that breaks the boulders into small pieces. Luigi then jumps in and whacks a piece of boulder back toward Czar. He gets hit and roars loudly.
He then creates a wall of flame and sends it toward our heroes. He is using the magic move Flame Wall. There is no way to avoid it, so the heroes take the hit, but thanks to the fire garb, they take little damage. Czar gets angry and begins to perform a very powerful move that he has mastered. He is the only fire being who can perform this move. He unleashes water blast. Very hot water starts to erupt around Mario, Luigi, and Mallow.
Mallow counterattacks by performing his own magic move called Snowy. The snow cools down the water, but our heroes still take damage. Mallow then performs his best magic attack, Star Rain. He raises his hands and many shooting stars come crashing down on Czar Dragon. He roars in pain and sinks into the lava.
Mario: Wow, how did you improve Star Rain?
Mallow: Pure practice.
Luigi: That was pretty cool, but we can move on now. We beat him.
Mario: No we didn't.
Luigi: Huh?
Mallow: Get ready, Luigi!
Luigi looks and sees the lava bubbling. Then, a boney dragon launches out of the lava. Zombone has been born.
Zombone: GWHOOOOOOOOOOOOOOOOOOOOOOOOOOOO!
Luigi: AHHHHHHHHHHHHHHHHHHHH!
Mario: This is what happens when Czar Dragon is beaten. He transforms into Zombone.
Mallow: And he is much tougher than when he's Czar Dragon.
Zombone: GWHOOOOOOOOOOOOOOOOOOOOOOOOOOOO!
BOSS BATTLE PART 2: Zombone
Zombone starts firing larger, faster fireballs. Mario smacks the ball of fire heading his way into nothing with his hammer. Zombone then performs a more powerful version of boulder. This time, Luigi and Mallow break the boulders and send the pieces back at him. Zombone roars and sends more fireballs at them. Mallow jumps in and uses a new move he has been working on called Hurricane. Mallow whips up a rainstorm along with a tornado and sends it at the fireballs and Zombone. Zomebone takes a great deal of damage and roars louder than ever before.
Zombone then begins to glow. Lava then starts circling around him. It then rises up into the air and erupts. Zombone is also using a move he has mastered: Eruption. Lava begins raining in the room and is piercing through the fire shirts and pants that Hinopio gave the heroes. The lava eventually knocks the heroes to the floor, making them motionless. Zombone laughs and is about to finish them by causing the volcano to erupt in the room they are in. He begins to glow once more. Is this the end of our heroes?
***
Outside, on top of Barrel Volcano, King Boo appears along with Bowser, who is incased in ice.
King Boo: Oh Bowser, you look so lovely inside that block of ice. Almost makes that painting of Mario I had back when Luigi tried to stop me look like just a frame. But, too bad you will eventually thaw out and try to stop me. That’s why I'll have the volcano take care of you. And not a moment too soon. Sounds like the volcano is going to erupt. So long, Bowser!
He drops Bowser into the volcano.
King Boo: Now, my Kingdom awaits me, along with my princess.
He disappears, laughing at the deed he just did.
***
Back in the volcano, Zombone is about to make the volcano erupt. The volcano starts shaking and the heat begins to increase. Above him, the block of ice King Boo threw in begins to melt. Eventually, Bowser breaks free.
Bowser: Yes! Free at last! Wait... Why am I falling?
He looks down and sees the lava Zombone is about to unleash.
Bowser: Uh oh... WHAAAAAAAAAAAAAAAAA!
Zombone is about to cause the volcano to erupt. But then he feels drops of water. He looks up and sees Bowser falling, shell first.
Bowser: WHAAAAAAAAAAAAAAAAAAAAAAAAAAAAA!
His shell hits Zombone's head, and Bowser bounces off his head into the cave behind Zombone. Zombone's head begins to crack. Then, his whole body begins to crack. He then bursts into a million pieces. Bones fly everywhere, and three hit the heroes' heads, which causes them to come to and look around to see what happened.
Mario: ... What in the world just happened?
Luigi: How did he burst into millions of bones?
Mallow: I don't know, but look now!
Mario and Luigi turn their heads to see that behind where Zombone was, there is a bridge leading to a cave.
Mario: Let's-a go!
The three of them head across the bridge and enter the cave. Inside, they find Bowser laying on his shell and trying to get up.
Mario: Bowser?
Bowser: Huh? Oh great! Just what I need, first King Boo, now you! This is not my lucky day!
Luigi: You too?
Bowser: Yeah! Wait... what do you mean by that?
Mario: King Boo beat us too.
Bowser: Really? How?
Luigi: Lightning.
Bowser: He beat me with ice!
Mallow: I thought King Boo could only lick, disappear, and breathe blue fire.
Bowser: Mallow?
Mallow: Yeah, it's me. Let the insults begin.
Bowser: Okay, one, I'm too tired to insult any of you, and two... HELP ME GET UP!
Mario: Are you going to attack us, then?
Bowser: NO! I already said I'm too tired.
Mario and Luigi approach Bowser and help him up from his back.
Bowser: Um... thanks, I guess.
Mario: No problem. Now, it looks like King Boo has really gone all out. I mean, he beat us AND Bowser. He can now use lightning and ice. Who knows what else he can now use? So the only way to stop him and save the kingdom AND the princess... is to team up.
Bowser: OH NO! Not again! We might have teamed up to stop Smithy, and Count Bleck...
Luigi: Actually, it was Dimentio who we stopped.
Bowser: WHATEVER! I am NOT teaming up with you guys again! I'll just go back to the castle and get my kids and minions to help. That should be enough to stop King Boo.
Bowser gets up and walks away, but then Mario gets an idea.
Mario: You know, I wouldn't be too surprised if King Boo pulled off the same trick Fawful did. You know... takeover your castle!
Bowser: ...
Mario: Yeah, right now, he could be there redecorating, and could've captured your kids and minions and thrown them in the dungeon.
Bowser: ...
Mario: But, who knows?
Bowser: ... Okay. I'll join.
Mario: Good. Now, shall we shake?
Mario extends his hand. Bowser hesitates, but then reaches out and they shake.
Bowser: You know, the more I think about joining you, the more I realize that King Boo has been an ex-Koopa Troop member ever since I fired him after the Isle Delfino incident.
Luigi: There, that’s a good way to get used to us.
Mallow: All right, we’ve got a new member, now lets get out of here.
They turn to leave, but then see a bright light.
Mario: Wh...what is that?