Easter Eggs are surreptitious references, mysteries and bonuses scattered all around Granny's House, even on the outside of it. All of them are listed and described below.
Main Easter Eggs
You can see all of the easter eggs here since Version 1.8.2.
Slendrina's Mother
It was added in Version 1.5, and changed in Version 1.7.9.3.
If you flip a switch behind a painting in the second bedroom, a bookshelf will move to the side and a secret room will be revealed. In this room there is a Lectern. If you put the Book on it between versions 1.5-1.7.9, the strange substance on the wall disappears and you can see Slendrina's Mother hung up on the wall with chains around her arms. As of Version 1.7.9.3, Slendrina's Mother will break free from her chains and begin to crawl. Since Version 1.8, you need to activate this Easter Egg if you want to escape Granny's House, because Slendrina's Mother will spew the Spider Key out, giving you access to the Spider Cellar.
The Bloody Message in the Drawer
It was added in Version 1.0.
In the left drawer of the Starting Bedroom, there is a bloody message written by the Previous Victim, "Leave this house"
Slendrina
It was added in Version 1.3.
If you deliver the Teddy to the Crib, without being caught by Granny, Slendrina will appear next to the Crib. After a few seconds, she will disappear, which will then give you the Secret Ending, if you escape through the Main Door. This is furthermore explained in this page.
Bloody Message in Brick Wall
This is exclusive to Version 1.4 and Version 1.4.0.1
If you go to the Garage and lift the Garage Door, you will see a message stating: "You can not escape!", this was most likely left by the Previous Victim, but, this is maybe just a troll placed by Granny.
The Shed Secret Message
It was added in Version 1.3.
If you somehow manage to get on top of the Shed, you will be able to see the message "HELP". The message is covered in blood, and is likely the Previous Victim's way of trying to communicate, and ask for help. It is unknown on how he got on top of the Shed.
The Note
It was added in Version 1.3.
If you go into the Dirt Room, on the table, there will be a Note, it seemingly looks like a piece of wood, and the message itself is all bloody. It is left by the Previous Victim, and is likely to help anyone else who gets trapped in Granny's House. The Note reads:
"This is my fifth day in this house. She chases me wherever I go. I'm quite injured and my body hurts. The only thing I remember before I woke up in this house is that I was driving when my car suddenly broke down. I went out to see what the problem was when someone suddenly hit me in the head. I have managed to open a pair of locks on the front door but that's all. Why does she do this? I hope no one will experience the same thing as I do. If I do not survive this and if someone find this message, I have noticed that she sometimes hides things inside fruits."
Slendrina Secret Ending
It was added in Version 1.3.2.
If you escape through the Main Door after delivering the Teddy into the Crib, you will get a whole other ending, Granny will sit on the porch holding the Teddy, and Slendrina will appear in the back, just standing there. After this is done, you won't get jumpscared by Granny, like you do, if you escape through the Main Door regularly.
Strange Substance
It was added in Version 1.5, and removed in Version 1.7.9.3.
The Strange Substance is an object in Granny that was located inside of the Bookshelf Room, for a period of time. The appearance of the substance is not very clear, it looks like a dark-yellowish wall with points that have a lighter-yellowish color. It looks old and disgusting. It seems like it has little "blots" all over it. The Strange Substance can be moved away using the Book, which then reveals Slendrina's Mother, chained to the wall.
Slendrina in the Introduction
This is exclusive to the PC Port of Granny.
At one point into the cutscene, the player turns to his left, revealing Slendrina in the far distance. She can be seen between the two trees, just standing there... M E N A C I N G L Y!
The Bonus Day (Day 6)
It was added in Version 1.2.
This is exclusive to Practice Mode. Easy Mode and Normal Mode.
Whilst playing in any of the three difficulties mentioned above, in the Basement, more specifically on the Workbench, there's a picture frame, with an empty canvas. It is found next to the Tin Can and can be assembled using the Painting Pieces. When assembled, you will be rewarded and given a bonus day from Granny. A message will appear on top of your screen, reading "Granny has rewarded you with a bonus day in the house.", which means you get a sixth day in the house. This isn't completely necessary, however.
The Scratch Marks on the Tables
It was added in Version 1.0.
The Tables in the Kitchen and the Starting Bedroom both have the words "FIVE DAYS" scratched/carved on their tabletops. This is likely left by the Previous Victim to alert the Player they only have five days at Granny's House, or to simply remind themselves.
Slendrina's Mother head is moveable
It was added in Version 1.7.9.3.
When you shoot the head of Slendrina's Mother with the Crossbow, her head will bob around a bit. It is unknown why this was added.
Trivia
- The Strange Substance and the Brick Wall are the only Easter Eggs that have been removed.
- The Slendrina's Mother Easter Egg is the only Easter Egg need for finishing the game.
- In the PC Port, Slendrina appears in the Introduction , which is Easter Egg too.