Ultimate Custom Night

The game allows the player to choose from 50 characters from all six main Five Nights at Freddy's games and FNaF World, and set their difficulty levels for the night from a minimum of "0" to a maximum of "20". During the night, the player must keep track of several mechanics, such as doors, ventilation systems, and air duct systems to avoid being attacked by the animatronics. The player can earn "Faz-Coins" to buy power-ups and deflect animatronics, and a "Death Coin" to eliminate a certain animatronic from the current night. The player is also able to select the office setting, choose power-ups that may help them during the night, and select 16 challenges available to them. The objective is to survive from 12 AM to 6 AM, with each hour in-game lasting 45 seconds.[1] In the final release, 59 characters from the franchise were included, with some appearing without the player's choice.

Although the game seems to be non-canon to the franchise, many elements in the game suggest that it might have a canon plot. After the player dies by certain characters, they speak certain lines that suggest that the player might actually be William Afton's soul trapped in a purgatory-like state after being burnt in the previous installment, tortured by various animatronics as consequences of his actions. Some of the speaking antagonists mention an unknown entity, referred to as "the one you should not have killed", who is thought to stay with William Afton to torture him. The entity is widely regarded to be the spirit living inside Golden Freddy because, after unlocking every intermission cutscene, a cutscene of Golden Freddy, twitching and surrounded by darkness, is shown. A rare screen also shows an obscured face of a small, grinning child thought to be the "vengeful spirit". During the night, if Old Man Consequences is set to "1" and all other characters are inactive, then, after catching a fish, a scene from FNaF World will be shown, with Old Man Consequences talking to a bear sprite (possibly Golden Freddy), telling him to leave the "demon" (Afton) to his own demons and rest in peace. It's implied that the other children's spirits have already moved on, but Golden Freddy refuses to do so.

However, the anthology novel series Fazbear Frights implies that the game is actually Afton's repeating nightmare, and not hell or purgatory. This is implied in the fifth book, Bunny Call, which has a story called "The Man in Room 1280" where a burned man is kept alive by a shadow child despite the fact that he should be dead and suffers nightmares. In the following book, Blackbird, the epilogue confirms that the man is actually William Afton. Although it was never confirmed if the Fazbear Frights series is canon or not, Cawthon confirmed that it's supposed to reveal mysteries from the previous games.

In February 2018, after the release of Freddy Fazbear's Pizzeria Simulator, Cawthon announced in a Steam post that he would think about gaining help from larger publishers in making future games.[2] In an edited version of the same post, he added that he would be developing an "ultimate custom night" add-on for Freddy Fazbear's Pizzeria Simulator, which, as revealed on his website, would have more than 50 animatronics from the entire series attacking the player. After some time, he decided that it would be too big an update for the game, so he made it a separate game. As he was programming the characters in the game, he would update the "progress bar" on his website, along with a brief description of the characters on a Steam post.

Rock, Paper, Shotgun deemed the game "an intriguing mess",[3] with PC Gamer calling it "a neat, customisable take on the classic survival horror formula".[4]