Easter eggs in the Little Nightmares series

Throughout the Little Nightmares games, players may notice Easter eggs and references left by Tarsier Studios. Some of these secrets are listed below.

Easter eggs in Little Nightmares

At the very beginning of Little Nightmares, when Six wakes up in a large suitcase, players may notice black-and-white photos on its lid, one of which shows a strange figure. The exact same photo can also be found in the ventilation leading to the Shoe Monster's room, and in a secret room with a Nome to hug. This figure is a Metrognome, characters from the cancelled game, The City of Metronome, developed by Tarsier Studios. A promo was used specifically for the photos, which shows a Metrognome selling teeth. Also in the Lair, in one of the rooms where the Janitor stores toys, on the top shelf under a strange painting you can see a Jack-in-the-box with a Metrognome's head.
In the children's room of the Prison on a chest of drawers, Six can find a music box that will start playing when touched. The tune it plays is a rendition of Prison Toys, recorded by composer Tobias Lilja, who wrote the music for the game.
In the secret room with a Nome next to the room with a sweeping eye, you can see an oscilloscope box, a device seen in Statik, a VR game released by Tarsier Studios in 2017. The box can be seen above and to the left of the Nome.
At the beginning of the Lair, when Six has to go up some long stairs to the Janitor’s apartment, she can go into an office, through which you can enter a secret room. To do this, put a chair on one of the tiles, after which the door will open in the closet. Behind it you will notice a huge eye-camera, with which you can inspect some of the rooms of the Maw by pressing the button several times. After you click on it after examining the Lady's Quarters, the eye will close. Click the button again for the Eye to show the mirror Six will use later on to defeat the Lady.
While under the floorboards of the Janitor's toy room, you may be able to see him reach into one of the shelves, pull out a rusty spoon and begin rubbing it with one finger. This is very possibly a reference to David Firth's 2005 video series, Salad Fingers, in which the titular character is shown to enjoy the texture of rusty spoons.
As part of the story, it is necessary at one point for Six to distract the Janitor with the help of a TV. If she presses the button several times, the screen will show strange images until, after some interference, a strange figure appears, approaching a sleeping child.
After escaping the Kitchen, if the player moves fast enough, Six can grab a fish that is sliding down the pipe and eat it.

Easter eggs in Secrets of the Maw

In the Hideaway, when the Runaway Kid descends into a coal warehouse in search of Nomes, he will need to lower a minecart onto the rails to open the doors that prevent the continuation of the game. If you go up the ladder and to the left, you will be able to find an eye camera similar to the one in the Prison. The Runaway Kid can inspect some places that Six visits during her escape from the Janitor. With the last click, the eye will show the Shoe Monster's room, where Six can be seen wading through the shoes. This heavily implies that the Runaway Kid's journey happens at the same time as Six's.
In the Residence, in some rooms, the Runaway Kid can find paintings depicting strange creatures, among which are the silhouette of a tall man, a man with thick lips, a woman in a school uniform, and children with broken heads. These turned out to be characters that Mono and Six meet in Little Nightmares II, while the portraits shown during a puzzle depicts more prominent antagonists from the game, such as the Doctor and the Teacher.
In the Residence, in the room with the eye and statues you can find a hole in the wall and behind that wall a hidden room with an bottle. This room have three statues with bowls and in one of the bowls is a radish. This is implied to be a tribute for the game Zelda: Breath of the Wild.

Easter eggs in Very Little Nightmares

In the Pretender's children's room, you can find a magazine with an image of the Maw on the cover.
In the Pretender's chambers, The Girl in the Yellow Raincoat must safely lower a Nome from the closet. To do this, she needs to go to the shared toilet and open the lid of one of the toilets. From which, a red balloon will immediately fly out, a clear reference to the movie It.
In the main hall of the Nest in the corner of the walls, the heroine may notice a picture of the Hanging Man, known to us from the first Little Nightmares game.

Easter Eggs in Little Nightmares II

There's a secret room near the collapsed bridge section in the Wilderness chapter where there will be a body buried by dirt and rocks with a shovel stuck onto it. This could be a possible reference to the infamous Dark Souls bonfire Easter egg.
Mono is able to open the refrigerator in the kitchen of the Hunter's shack. However, if the player mods the game, the player can see some cans with the Twin Chefs' face as brand covers.
In The Nome's Attic DLC, the player is able to find a broken porcelain doll identical to the statues found all throughout the Maw .
At the end of The Nome's Attic DLC, the player can see what appears to be a poster of the Maw covered by leaves on the floorboards if the game is modded. This poster can also be seen in the secret ending of the game.
At the bottom corner of the beach before you enter the Pale City, a watermelon is buried in the sand. This is an Easter egg and tribute to the secret ending of the game ICO.
Pictures depicting the Fat Kid and the Ghost Child from Little Nightmares Comics are seen throughout the Pale City.
Among the drawings made by a punished Bully, you can see references to the first game, such as the Janitor, Nomes, and the Maw. These drawings can be seen more clearly when the game is modded.
In a room inside the School's cafeteria, there is a dead cook. She is the Lunch Lady, who is supposed to be an enemy encountered in the said area but is cut before the release of the game.
Just before Six finds the yellow raincoat, a paper boat can be found next to a storm drain, referencing to the It series.
In the same room where Mono finds the flashlight, there is an oscilloscope box on a wheelchair, which is a reference to the game Statik.
In the Patients' corridor section of the Hospital, Mono can go through a gap that is located at the back of the door of the room he first entered. Afterwards, Mono can go to the door behind the bars and find a room with tallies all over the walls. There's also a visible hole located in the middle of the room. If Mono brings the cheese and throws it down the hole, a mysterious crunching noise will occur. In the third episode of Little Nightmares Comics, it is revealed that a girl used to be trapped in this room and later broke out of it through the hole she dug with numerous spoons. If other objects such as a tin can is thrown into the hole instead, the mysterious creature will throw it back out.
The bus stop signs in the Pale City, especially the one located in an open area after Mono and Six have escaped the Hospital, are implied to be a tribute to the studio Ghibli film My Neighbor Totoro,
After Mono slides down with a coat hanger from the Pale City's post office, he can leave through the window of the room he had just broken into, and make his way to another room via the roof. In this rather neat room, the player can see the Lady's portrait in a picture frame, and a Lady statue. This room may be either the Lady's former residence, a random citizen's residence, to show how well-known the Lady is in the Pale City, or simply just a reference to the Lady herself.
While accomplishing the post industrial achievement, an unknown resident can be briefly observed reaching their hands through a mail slot to obtain the package Mono carries. This Easter egg cannot be triggered if Mono is wearing other hats.