During development the animatronics' names, Bonnie, Chica, Foxy, and Freddy were just placeholder nicknames before Scott Cawthon had decided on their "real" names.
Even though there is no specified year in which the game takes place, many have assumed that it takes place around 1993, as the paycheck matches the minimum wage of the time.
According to the game's creator, Foxy's character model was made during a 24 hour drive to visit family. He said it was a very bumpy ride and may be why Foxy looks so torn up.
Freddy wasn't intended to move around the diner, instead, Scott originally wanted him to get the player if his/her time ran out. This was changed before release.
In the game's trailer, Bonnie is shown removing his mask to reveal his endoskeleton head. However, this never happens in the game's final release.
On Night 5, Spoiler:instead of getting the usual message from the previous night guard (as it was revealed in Night 4's call that he was killed) the player will instead hear some deep garbled speech. When played backwards, it is revealed to be an excerpt from the book, "Autobiography of a Yogi", specifically the section about a scientist who is discussing his theory about plants, animals and metal having a similar life force.
Graphics exist of an unused design for the cameras on the monitor, giving a more precise location as to where they are. They also show earlier locations for some cameras prior to the game's final locations being decided upon.
The song that Freddy plays is "Votre toast, je peux vous le rendre"; also referred to as "Toreador March".
During the game's prerelease period, the player was given a set number of lives. This was removed from the final version, where the player only has 1 life.
Despite their names, both Bonnie and Foxy are male. This makes Chica the only female animatronic in the game. The name Chica is also Spanish for "girl" or "cutie".
The third star is only obtainable by completing the 7th night on 20/20/20/20. The creator, Scott Cawthon, put in the third star after seeing YouTuber 'BigBugz' complete the night, as he thought it was impossible.
In the main office, you can see a poster on the wall directly in front of you that says "Celebrate!". Clicking on Freddy's nose on the poster will make a honking noise. This does not affect the game at all, and is just there for fun.
Setting the levels of the AI to 1/9/8/7 on the custom 7th night will cause Golden Freddy to appear automatically in your office. This was likely added to prank players, as a number of rumors were spreading around of a supposed 1987 mode.
In the game's announcement trailer, Bonnie can be seen running down the hall. In the final game however, Foxy is the only one that can actually be seen moving.
When checking the W. Corner Hall camera (2B), the player can see a poster on the wall. The image it displays is random, but once in a while it shows a close up of a golden-coloured Freddy Fazbear. After which, when the player returns to the security room, an empty golden Freddy suit will appear in front of the player. If the player does not change camera to a different room, Golden Freddy's face will attack the player and crash the game.