When you complete the game and viewed the credits to the end allow the game to idle after the book closes and the light turns off. After several minutes a lullaby song will begin to play until you press a button.
When you paperize the area around a circle of flippable flowers a stickable area will appear. Place a sticker and a '?' block will appear. Inside the block will be a more powerful version of the sticker that you originally used.
Search the following background locations to find Luigi in the background. When you have found Mario's brother and peeled him off ALL five locations by Paperizing he will become unlocked in the credits sequence. Each time you peel off Luigi, you can read an amusing newspaper article in the leftmost house in Decalburg's Residential Area.
World 1-6: On the bridge leading to the central tower (search the background).
World 2-5: On the fourth floor of the tower, in a window at the far right end of the second outdoor walkway.
World 3-12: On a rock formation sticking out of the ocean that is only visible from the pier.
World 4-5: Near the end of the chairlift after the enemies stop coming; appears only briefly.
World 5-5: In the background to the left of the hot springs.
In World 3 the Wiggler's segments are scattered and you need to 'subdue' and take it to the indicated location to unlock the diary entry. You must have ALL Wiggler Diary entries before returning the fourth segment to Wiggler or else they will no longer be available to be found.
Surfshine Harbor: Obtained automatically.
World 3-2: Through the dandelion in the area before the Comet Piece so that it scatters.
World 3-6: Overlook to the left of the shop.
World 3-8: Poisoned hot springs.
World 3-10: Replay the game show while the segment watches (the bonus round can be skipped).
Except for Megaflash Hurlhammer (which appears in two) the following Megaflash stickers which are the rarest and most powerful battle stickers in the game will appear in the indicated location. When you find the location of a Megaflash sticker you can get as many of that sticker as you want there.
Megaflash Hammer: World 2-2: Behind a secret panel below the balcony in the room with the Hammer Bros.
Megaflash Line Jump: World 4-6: On a ledge below and to the right of where you fight the boss. Return after getting the Royal Sticker.
Megaflash Chillhammer: World 4-6: On a platform in the second minecart area that requires you to Paperize the rail to reach.
Megaflash Hurlhammer: World 5-1: Behind the Hammer Bro in the area with the second red flower.
Megaflash Infinijump: World 5-3: In a secret area to the right of the pillars in the room with the Comet Piece that's accesible from the 'loop' in the river.
Megaflash Eekhammer: World 5-4: At the beginning of the level, hit the stake with the hammer to release the raft, then ride it to the right.
Megaflash Hopslipper: World 5-4: In the same room as the Megaflash Baahammer and Megaflash Hurlhammer.
Megaflash Hurlhammer (2nd Location): World 5-4: In the same room as the Megaflash Baahammer.
Megaflash Baahammer: World 5-4: On the third floor, through a warp pipe hidden to the right of the moving platforms in the main room.
Megaflash Burnhammer: World 5-5: In the first area, in a secret room behind a rock near the entrance to the second area.
Megaflash Iron Jump: World 5-5: In the fifth area, under the 'X' at the top of the hill. Stand on it until you see a shadow, then move out of the way.
Megaflash Slaphammer: World 5-5: In the fourth area, under the 'X' on the ground closest to the entrance. Stand on it until you see a shadow, then move out of the way.
Megaflash Clone Jump: World 5-6: On the third floor, pound the stake furthest to the right.
Megaflash Jump: World 6-2: Through the Secret Door, in the ship's cabin.
There are a total of eight Achievements that you can earn in this game, all of which can be achieved at any time by completing the corresponding task. Note: after completing World 1-6 and getting the first Royal Sticker, there are eight Super Flags in the Sticker Fest area of Decalburg. These can be examined to view your progress in unlocking the Achievements.
Super Flag Achievement: Collect ALL of the Comet Pieces.
Super Flag Achievement: Find every single HP-Up Heart.
Super Flag Achievement: Make ALL of the secret doors appear.
Super Flag Achievement: Spend 10,000 or more Coins at shops.
Super Flag Achievement: Perform 1,000 or more 'Excellent' Action Commands in battle.
Super Flag Achievement: Get three symbols matched on the Battle Spinner slots 50 times.
Super Flag Achievement: Get a Perfect Bonus (win without getting hit) in 500 or more battles.
Super Flag Achievement: Collect every sticker type in the world.