Golden Freddy/Canon

Golden Freddy is a mysterious antagonist who debuted in the first game. He's a golden and slumped version of Freddy Fazbear and is likely a ghost.

Five Nights at Freddy's
WIP

Five Nights at Freddy's 2
Golden Freddy has a different design in this game to match Withered Freddy's. He only appears in Night 6, either in the office or as a giant head in the hallway. His behavior is more complex this time, if he's in the hallway, the player must simply turn off the flashlight, otherwise, the only way to prevent him is by putting on the Freddy Fazbear Head as quickly as possible.Unlike in the previous game, his AI can be altered in Custom Night. He also doesn't crash the game, instead causing a simple game over.

At the end of the Give Gifts, Give Life minigame, a fifth body can be seen in the middle of the room for a single frame and the player will be sgreeted by a Golden Freddy jumpscare righty after. He can also be encountered throughout the building in the S-A-V-E-T-H-E-M minigame, if the player approaches him, his eyes will light up and he will disappear.

Ultimate Custom Night
Golden Freddy re-appears as a selectable enemy in Ultimate Custom Night with the same basic behavior as in the past games. Using his FNaF2 design, he will randomly appear in your office and the player must either put on the mask or flip up their monitor quick enough or they'll get a game over, the higher his AI is, the more often he will appear. If the player sets Golden Freddy's AI to 1 with everyone else deactivated and uses a Death Coin when he appears, it will trigger a Fredbear jumpscare.

Golden Freddy also appears to play a large role in the story of this game, as the last cut-scene that can be unlocked shows his original design shaking and slowly fading away into a black void.

Theories
The identity of the Golden Freddy spirit is highly debated, at first, it was mostly agreed on that he was simply one of the five kids mentioned in the newspapers from the first game. However, many people now believe him to be the protagonist of the Five Nights at Freddy's 4 minigames, based on the text saying he'll be put back together in the final minigame. Him getting his head crushed by Fredbear would explain why the spirit takes the form of a yellow Freddy.

Most people agree that the spirit is "the one you shouldn't have killed" mentioned by multiple characters in Ultimate Custom Night, as well as the mysterious boy face that rarely appears in the vent or in the game over screen, indicating the kid is likely male.

Some people believe him to be an actual, physical suit, as well as the yellow suit mentioned by Phone Guy in Five Nights at Freddy's 2. Others argue against this by pointing out his ghostly attributes, how he can teleport, vanish and turn into a giant head.