1. Red Glowing Dice - in Optical in the room where you pick up a giant painted green king chess piece. Use the block and king to get into the upper room. The dice can be found in the trash. There is a small hole in the floor in the corner on the left of the trash can. If you make the dice very small and throw it in this hole, the dice will respawn in the trash. When dropping the dice anywhere it attempts to have the chess piece on it face upwards, usually not following normal physics to achieve this.

2. Golden Bishop - in Cubism in the dark room under the floorboards. Falls very slowly when dropped in the air.

3. Rubber Duck - in Cubism after the "pulling cubes" room there is a darker room with a tower of pallets on the right side and a bucket where water drips. Inside the bucket there is a rubber duck which bounces and squeaks.

4. Green Apple - in Clone in the room with a multiplying apple and fan. Occasionally when multiplying the apple it will change colour to be slightly more yellow. Multiplying the new yellower apple and repeating this will eventually lead to a green apple.

5. Glowing Apple - in Clone in the room with a multiplying apple and fan. After multiplying the apple a lot, near the limit of how many times you can multiply it, a glowing apple will appear. Multiplying this glowing apple produces more glowing apples. Letting some normal apples be blown into the pit by the fan allows more duplicates of the glowing apple to be made.

6. Banana - in Clone in the room with the Somnasculpt signs. High up on the left of the room there is a potted plant with a banana growing on it. This banana rotates to a particular orientation when falling, and when dropped on the floor always causes a loud noise and a shudder regardless of its size.

7. Avocados - in Dollhouse in the hallway just outside the starting room. Located in Suite C door, see Secret Rooms section for info on how to access this room.

8. Casino chips - in Dollhouse with the dollhouses, in the room where you need to go through a keyhole, bring both portals with you to the next room where the chessboard is. Use the portals to get to normal size. In the far end of the room to the left there is a table with a blue organizer and a white mug, Behind the mug there is the chip which clones itself.

9. Top - in Whitespace in the room with the light switch, on the top of the broken chess piece.

10. Banana - in Whitespace in the area with the massive water coolers, if you walk around the top of the barrier, there is a banana wedged in a corner. Unlike the banana in Clone, when you let go of this one it flies toward you.

Induction: In the room with the boarded-up door you can pick up and remove the planks and enter the hallway. You cannot go anywhere since the door is fake, and the Standard Orientation Protocol will tell you that you have deviated from the orientation pathway. This is likely because (at the time) Dr. Glenn Pierce probably didn't want people to notice these areas, although that is worthless in any other level.

Optical: Found in the room with the giant, cyan king piece. Once aligned and able to be interacted with, the checkered cube and the king piece can be used as steps to reach the overhead doorway. It leads to a hallway with pink wallpaper. At the dead-end there is a trash can with a glowing, red dice inside. Entering this room grants the Please Use the Other Door achievement.

Optical: Found in the room above the moon room. Using the object/s on the moon (the can, cheese, building block and/or doorway), the player can reach the opening in the skylight. This has the contents of a usual behind-the-scenes room: spare wall panels, traffic cones, spotlights, a carpentry workbench, etc.. Unique to this room, there is also six projectors that create the illusion of a night sky. They can be switched on and off, as a single unit, by the player. Additionally, a blueprint can be found here.

Cubism: Found in the room with the dice that splits into halves. This room is partially visible in a gap between the two almost-intersecting wall panels. The room can be entered by going over a panel using the dice halves as steps. Nothing is in the room except for a water dispenser. Exiting the room is difficult and a level restart may be necessary.

Dollhouse: Suite C door, found in the hallway just outside the starting room. Includes a radio with a message that doesn't appear anywhere else, and 3 grabbable avocados. Grabbing and dropping the avocado found on the bed causes it to split into halves, releasing the core inside.

Dollhouse: Suite E door, found just across from Suite E door. Includes a radio with a message that doesn't appear anywhere else.

Labyrinth: After the looping hallway puzzle, grab the cube from the pool room without entering the room, use the cube to get back up to the looping hallway puzzle, then walk as far back as you can. Once you stand below the high up door you'll be sent to "HALL 06" where no matter which direction you go you continue to loop back into HALL 06. This is most likely a bug as it softlocks you.

Labyrinth: Found shortly after the room where the yellow queen flattens after being interacted with. In the hallway right after, there is a hole in the floor you fall through to continue the level. Fall through this hole and carefully land on the trashcan, then jump up into the secret room. There is unfortunately nothing of interest in the room.

Whitespace: Found in the first room of this level with the bed and acoustic foam on the walls. The level must be completed before this room is accessible. Before the secret room can be entered, go into the model room and walk through the hallway at least once (to establish the teleportation between doorways). Now, to enter the secret room, place the same model room back on the table, taking care it's approx. the same size as the other two models. After exiting the hallway, the player is now small enough to enter the rightmost model, labelled "Jungles' Bistro", through a door on its back. It looks like a usual bistro with a stage, a bar and a dining area. On the stage there is a keyboard that the player can play. Also notable, is the bar whose shelves hold only cans found in the Dream Soda vending machine.

Whitespace: After all 15 chess pieces are collected, you can walk up to the monitor at the start of most levels and click on it. This will take you to a room with a chessboard where you can obtain the Kasparov hidden achievement.
The board configuration shown in the monitor/room is the penultimate position from Garry Kasparov's first game against the IBM supercomputer Deep Blue in 1996. The move that needs to be executed to gain the achievement was Deep Blue's final winning move in this game, which was the first time a computer defeated a world champion at chess under normal tournament conditions.
You can jump out of one of the windows in the chess room, ending up in the middle of Whitespace in the courtyard surrounded by blank white buildings.

1. Induction: After the room with the cheese ramp, there is a hallway with a window filled with alarm clocks that say 12:05, except for six. Going left to right, one can find six alarm clocks in the window that say 4, 8, 15, 16, 23, and 42 (you may have to jump to find some). This is a reference to the show Lost.
2. Optical: In the room with the distorted exit door there are two messages on the walls in the corners of the room. They read "Please don't snoop around" and "why are you doing this".
3. Dollhouse: In the room after the bouncy castle puzzle, a playable piano can be found hidden behind the door to the next area.
4. Labyrinth: After you fall towards the red pawn, walk into the dark area. You can find some cheese and a TV with an image from the Museum of Simulation Technology tech demo, which eventually became the game Superliminal.
5. Labyrinth: In the room where the yellow queen flattens after being interacted with, the light shining down on the alarm siren on the wall makes the shadow look like a pawn.
6. Whitespace: In the first room of the level, faint music emanates from the wall covered in sound proofing.
7. Whitespace: In the apartment area with the secret chess room, there are 8 letters spread around on the buildings. Putting them together makes the phrase "DEEP BLUE" which is a reference to the Deep Blue chess computer.
8. Whitespace: There is a child's drawing in the water dispenser room. It appears first as nothing but a white rectangle, but clicking it changes it to the drawing. Clicking it again changes it into the artist's signature. The developer's commentary states that a six year old fan named Scout (Who notably was a fan for his 'lifetime'), presented the drawing to the developers at a PAX conference, where they had a playable demo. Scout played the demo, and was so excited by it he made the drawing and returned to the conference to present it to the developers the next day. This is their first piece of fan art, and they decided to immortalize it in the game.
9. All levels: At the start of levels where you wake up in Suite F, on the bulletin board in the hallway you can find a piece of paper with some code which provides insight into how SOMNASCULPT works.^[1]
10. All levels: Bringing certain objects into star rooms causes them to glow. Bringing the white king or the egg in Whitespace into the level’s star room causes them to glow. Also in Whitespace, the flying banana mentioned in the secret objects section will glow as well. The same thing can be done in Optical, this time with an exit sign.
11. Main Menu: Flipping all of the fire alarms in the game causes a button to appear on the menu in the shape of a fire alarm. Clicking this causes particles to rain from the ceiling into the room shown on the menu.
12. Main Menu: After completing every constellation room, a button in the shape of an exit sign will appear on the main menu options, as well as a projector displaying the moon that will appear in the room shown on the menu. Clicking on the button causes you to load into the level shown on the main menu. Any changes you make while in the level will be saved when returning to the main menu, with the exclusion of the letters found in the adjacent room.
13. After using every fire extinguisher in the game, clicking on any of them causes fire to shoot out of it.
14. In the Developer Commentary mode, there is some unique dialogue near the end of the credits.