Secret Blue Doors are amongst the hardest secrets to uncover in Paper Mario: Sticker Star. There’s a Blue Door in almost every stage, hiding special rare stickers and Things. To open the doors you’ll need the Secret Blue Door stickers which can be bought from the shop in World 3-6. Be sure to buy a lot of them since there are many doors scattered around
- World 1
1-1: The Blue door is hidden under a sign with the Hammer Sticker: paperize the blue door sticker on the outline and get the Thumbtack Thing.
1-2: Close to the level’s end, there’s a platform with the Sticker Comet and the door outline: open the door and grab the Flashy Ice Flower Sticker, Flashy Fire Flower Sticker and the Flashy POW Block.
1-3: Remove the Faucet for a second time: after the water is gone you’ll be able to jump into the hole. Once in the underground you’ll notice the door outline immediately. Inside the blue door is a Bed Thing.
1-4: Just before the end of the stage, after getting out of the red pipe, you’ll notice the door’s outline on the wall behind you: paperize the sticker and get the Matches Thing.
1-5: Take the warp pipe near the beginning of the level. Once underground move on and you’ll see the door’s outline halfway through the path. A Bellow Thing awaits behind the Blue Door.
1-6: During the fortress segment two fans will move you off the bridge, where a door outline awaits you: it’s close to three blocks. Inside the Secret Blue Door is a Squirt Gun Thins.
- World 2
2-1: Get to the top of the Pyramid and get to the back of the structure once near the top: a Shy Guy is in front of the door’s outline. Defeat him, paperize and get the Car Battery Thing.
2-2: Get to the back of the Sphynx and together with a HP up heart you’ll see a blue door’s outline: the Paper Fan Thing awaits you behind it.
2-3: Go to the right 3 times when you reach the area with the sand waterfalls. You’ll get into a room with two entrances: to the left of this room is our beloved door outline with a Lighter Thing behind it.
2-4: This one is really hard to miss: keep going to the left and you’ll eventually see an outline. Paperize and get the Hair Shears Thing.
2-5: Another easy one: at the beginning of the stage you’ll see the door’s outline on the back wall. A couple of rare stickers await you: a Flashy Eekhammer, a Flashy HurlHammer and a Flashy Spike Helmet.
Article from Gamersyndrome.com