The bros have reached the pipe the Koopas went through to haul papercrafts. Cross the bridge and a Papercraft Bullet Bill nearly drops on the players. The Kameks appear, along with Papercraft Dry Bones and Papercraft King Boo. Lemmy Koopa and Morton Koopa Jr. control Papercraft King Boo. The Kameks want to settle things and the Koopalings want to stomp the bros. Paper Kamek thinks Papercraft Boo is menacing, but Kamek doesn't think it's the most menacing papercraft ever. Papercraft Kamek is disappointed that they won't get to use it because the bros don't have a papercraft. He starts envisioning it, but Kamek says they've got one ready to go. It's Papercraft Yoshi. The Kameks fall to the ground. Paper Kamek wonders how they snuck it into Bowser's Castle. Toadette says she built it here just now.
Papercraft Yoshi can do a ground pound when (A) is pressed in midair. Use it to hit switches or stun enemies when you land near them. Use (B) to stick out Papercraft Yoshi's tongue to grab things and tow floating enemies. Defeat enemies to make poles appear so you can cross the lava. Use the Starman to clear out the Papercraft Goombas. Make your way around to the largest platform and cross the bridge. Papercraft King Boo appears. There will be three Papercraft Dry Bones that will get in your way, so get rid of them. Papercraft King Boo will ground pound the area. Move out of the way, then attack when it's off it's pedestal. When Papercraft King Boo is at half health, it will summon two more Papercraft Boos. Papercraft King Boo will do a rolling attack. Dodge it and attack.
After the battle, the Kameks thought that Papercraft Yoshi was so good, they've decided to kidnap Toadette. They're also going to build the best papercraft yet. Go north. The bros enter a long hallway. Flames appear from the floor, preventing the bros from going north. There are Paper Boomerang Bros here, which are particularly dangerous, because the boomerang they carry can be another Paper Boomerang Bro. Go west. There's a Fly Guy holding onto Toadette. He starts to fly away. The bros have to defeat him before he does. Use Trio Glide to cross the lava. Use the fan blocks to turn them on and off. Catch up to the Fly Guy and battle him. Toadette thanks the bros for saving her. She decides to return to Peach's Castle. She looked around the castle and thinks the princesses are on the top floor.
The Bowser Jrs. are bored guarding two cardboard princesses. Paper Bowser Jr. wants them to try to escape to give him something to do. He also wants them to say something different. He tries to tell them Mario's not going to save them. He slowly starts losing it and decides to go outside. Behind the cage, the princesses spy their moment to escape. They decide to leave through a window. Bowser Jr. is sleeping, wondering why it's so cold.
Luigi is worried about Toadette, but she says she can take care of herself, having tracked a treasure or two. Hit the nearby Bowser Block to make one of the eyes in the floor close. Go through the pipe, return to the long hallway, and go east. There's a long path with many fans blowing the bros off of it. Dash at an angle to make it across safely. When you loop around, Trio Glide to left. Hit the Bowser Block and ! Block. This will open the door and make the flames disappear. Return to the long hallway and go up the elevator.
The bros hear Peach's voice. The princesses are outside, on a different part of the castle. They head back. Walk forward. The door is open. The princesses meet the bros inside, but Paper Bowser Jr. grabs them in his clown copter. The Bowser Jrs. lock them behind a door, calling it a dirty trick for them to sneak out when he was sleeping. He's going to tell Bowser. Paper Bowser Jr. wonders if the bros are there for the book or the princesses, giving away the fact that they've been holding it all this time. Bowser Jr. thinks both, but says they're never giving back the book. The Bowser Jrs. realize the bros didn't know they had the book. Starlow wants both the book and the princesses back. They don't want to, so they split up and run away. Go east and west to get some items and coins. The door to the princesses won't budge, so leave them for now.