There are 28 Memories to be collected throughout the various locations in the dream world. Once obtained, they will be displayed in the Memory Room and appear as a yellow square in the save menu. Each dot/square represents one memory.
Additionally, there are 7 items called Empties that are hidden throughout the dream world, typically found through invisible pathways or unorthodox solutions. Unlike Memories, they will not be displayed in the Memory Room and instead appear as an extra row of black squares with purple borders on the save menu. Each Empty has a brief effect on Muma's appearance when collected before returning her to the Memory Room.
Memories
Bubblegum
Appearance: A wriggling piece of chewed-up bubblegum.
Location: Found in the Memory Room during the game's tutorial.
Rose
Appearance: A red rose swaying from side to side.
Location: Found in First Steps near a black rabbit, slightly southeast of the Memory Room doorway.
White Square
Appearance: A hovering white square with a smaller black square inside of it.
Location: Found in White Shores in front of a door leading back to the Memory Room.
Coral
Appearance: A piece of bright red red coral.
Location: Found in the Undersea Expanse by riding the fish northwest of the ladder leading to White Shores.
Umbrella
Appearance: A purple and red striped umbrella with a red handle.
Location: Found in Rainforest Road by going through the gap in the fence and then heading left, down, right, down, and then heading right on the second road. Muma will always appear with the Umbrella equipped when entering the Rainforest Road after it is obtained.
Soda
Appearance: A red soda can with a white stripe down its side and OK written on it. If the OK Lemon poster has been viewed in Chicago, then the soda can will be yellow.
Location: Found in the Swimming Pool vending machine. Can only be obtained by first swimming in the pool, grabbing the gray coin from one of the lockers, and then operating the vending machine with the gray coin.
Snowglobe
Appearance: A snowglobe featuring a miniature brown house with a red roof depicted inside.
Location: Found in Pink Snowscape, located directly north of the igloo from Rainforest Road.
Beach Ball
Appearance: A white and blue striped beach ball.
Location: Found in one of the houses in Red Sands B, being played with by a small girl. Interacting with the girl will make her disappear, letting the memory be obtained.
Cassette Tape
Appearance: A cassette tape dripping with blood.
Location: Found in the Occult Basement in the middle of a pentagram after crushing the five hearts scattered around the basement.
Balloon
Appearance: A red balloon.
Location: Found on the top floor of the Monochrome Building, attached to the balcony.
Sword
Appearance: A silver, pixel art-styled sword with a golden hilt.
Location: Found in the Unicorn Woods after operating the arcade machine with a gray coin. Muma will always have the Sword equipped when she enters the Unicorn Woods after obtaining it. Allows her to slay the unicorn head enemies that appear in the world.
Winged Boots
Appearance: A shiny, brown, pixel art-styled boot with pink wings.
Location: Found within one of the southern rooms in the Cave Game near a face made of blocks. Gives Muma the ability to double jump in the Cave of Perils, making traversing some parts much easier.
Beating Heart
Appearance: A realistic pulsating heart.
Location: Found on a heart-shaped formation in Flesh n' Blood.
Empties
Memory Room's Empty
Effect: Static is flashed over Muma's body before she turns to face her hanged self.
Realm of the Orb's Empty
Effect: Muma is turned into a silhouette before pieces of her are scattered into the air, shriveling her away.
Blood n' Blood's Empty
Effect: Muma becomes completely red before she explodes into a mess of flesh and blood, her clothes falling to the ground.
Above the Clouds' Empty
Effect: Rainbows pour out of Muma's eyes, suddenly shaking violently before two more streams burst from her sides.
Retro Dungeon's Empty
Effect: Muma's appearance flickers between being her normal self and a white outline, then glitches into two copies of herself in different states.
Monochrome Building's Empty
Effect: Muma's eyes transform into a large red ovular pair with black scelera. Japanese あ symbols quickly shake around her as she screams.
Faraway Place's Empty
Effect: A hole forms in the middle of Muma's torso, from which black tendrils appear and completely engulf her.