Withers/guide

Wheelchair
Enter the top-left door to the Blood World. Go up and right from the entrance and enter the sewer hole to the Sewer. Go right and enter the door to the Staircase Maze. Interact with the wheelchair on the middle bottom part.

Drip Stand
Enter the middle-right door to the Ice World. Go north-west and find an ice building to the Ice Rooms. Go right, bottom, top to the faucet, interact with the faucet to the Green Field Room, exit the room and enter the rust entrance to the Rust Staircase and exit from a big faucet to the Water Surface, go left until you reach the hole to the Umbilical Cord Maze, enter the bottom-left path way then go straight left until you find a drip stand.

Camera
Enter the middle-left door to the Burned Ground. Head straight down until you reach a burned tree then go right until you see another destroyed building above you. Enter it and interact with the camera on the floor.

Muffler
Enter the bottom-left door to the Clover World. Head straight down until you reach a 3x3 square of sand and turn left. Keep going left and you should find an invisible NPC wearing a red muffler that you get the effect from.

Costume
Enter the middle-right door to the Ice World. Go east until you reach a tall ice building to the Ice Maze. Each time you reach a fork, choose bottom-right, bottom-right, top-right to a large land, then choose top-left until you reach the NPC that gives you the effect.

Harmonica
Enter the bottom-left door to the Clover World. Go north-west and between two intertwining pillars to the Brain and take the elevator to the Reflection Storeroom. Take the left path to the Brown Storeroom. Just keep going left until you reach the last room filled with boxes of dolls body parts and interact with the harmonica.

Guinea Pig
Enter the top-left door to the Blood World. Go up and right from the entrance then enter the sewer hole to the Sewer. Go right and down the ladder, turn on the light then go left to the Storage. Interact with the white monster on the left part.

Mushroom
Enter the bottom-right door to the Dark Mushroom Forest. Go right until you can go right then go up to a wide area with mushrooms surrounded by leaves. From here you can either enter the hidden passage on the top-left of the mushrooms then choose the left pathway on the fork to the Broken Egg House and interact with the red grass, or go straight right and through the hidden passage to a wide area with two mushroom pillars surrounded by mushrooms, go between the pillars to the Mushroom World, from the entrance go south until you find a pink mushroom then go south-west from the mushroom and interact with the red grass.

Flower Vase
Enter the top-right door to the Electronic Tube World. Go south-west to find a tube with electric symbol to the Tiles Pathway. Go through the way to the second part and choose the staircase on the right then exit to the Balcony, enter the entrance on the bottom-right to the second balcony then enter the broken fence to the Flower Vase World, go north-west to find the vase with a white flower.

Scarecrow
Enter the bottom-left door to the Clover World. Go north-west and between two intertwining pillars to the Brain and take the elevator to the Reflection Storeroom. Take the left path to the Brown Storeroom. Keep going left until you reach a doorway north of you. Enter it and go through the leftmost door at the end of the hall to the Wilderness. Head down from where you teleport and interact with the scarecrow.

Range
Enter the middle-left door to the Burned Ground. Go north-west and enter the staircase to the Underground Pathway, go right to the second pathway and go right, meet the graffiti on the wall about two times then turn left then go straight left to the Snow World. Go south until you reach the pipe then go west to find the range.

Hat and Scarf
Enter the middle-left door to the Burned Ground. Go north-west and enter the staircase to the Underground Pathway, go right to the second pathway and go right, meet the graffiti on the wall about two times then turn left then go left and enter the door to the Prison, enter the cell door on the center and interact with the hat and scarf on the floor.