Ultimate Custom Night is a horror game developed and produced by Scott Gogh, a spin-off of the Teddy Bear's Five Nights in the Harem series. The game includes 50 optional characters and custom difficulty! Spanning seven "Five Nights", the customization options are almost endless. Players must challenge and defeat more mechanical dolls to obtain a high score.

And here are a few new features: Challenge menu, including sixteen themed challenges.

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.

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". The full roster includes Five Nights at Freddy's characters Freddy Fazbear, Bonnie, Chica, and Foxy, Five Nights at Freddy's 2 characters Toy Freddy, Toy Bonnie, Toy Chica, Mangle, BB, JJ (a female version of BB that previously appeared as a hallucination), Withered Chica, Withered Bonnie, the Puppet, and Golden Freddy, Five Nights at Freddy's 3 characters Springtrap, Phantom Mangle, Phantom Freddy, and Phantom BB, Five Nights at Freddy's 4 characters Nightmare Freddy, Nightmare Bonnie, Nightmare Fredbear, and Nightmare, plus Jack-O-Chica, Nightmare Mangle, Nightmarionne, and Nightmare BB from the game's Halloween Edition, Old Man Consequences from FNaF World, Five Nights at Freddy's: Sister Location characters Circus Baby, Ballora, Funtime Foxy, and Ennard, and Freddy Fazbear's Pizzeria Simulator characters Trash and the Gang, Helpy, the Mediocre Melodies (Happy Frog, Mr. Hippo, Pigpatch, Nedd Bear, and Orville Elephant), the Rockstars (Rockstar Freddy, Rockstar Bonnie, Rockstar Chica, and Rockstar Foxy), the Posh Pizzeria (Music Man, El Chip, and Funtime Chica), Molten Freddy, Scrap Baby, William Afton / Scraptrap, and Lefty, with the last character being the Phone Guy. 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. Of these extra nine, Dee Dee from FNaF World, has the ability to randomly spawn and summon either a character that isn't currently active or one of six that are unavailable to the player, with a new form of her named XOR being able to summon all of the extra six. These six include RWQFSFASXC / Shadow Bonnie from Five Nights at Freddy's 2, Plushtrap and Nightmare Chica from Five Nights at Freddy's 4, Minireena and Lolbit from Five Nights at Freddy's: Sister Location, and Bonnet from that same game's Custom Night. An easter egg involving using the Death Coin on Golden Freddy when he's the only active character on a night and set to 1 triggers a jumpscare from Fredbear, the earlier incarnation of Golden Freddy who had previously only appeared in minigames.