On February 16, 2018, Scott Cawthon made a Steam post about a possible free update for Freddy Fazbear's Pizzeria Simulator, those being an endless tycoon and an ultimate custom night:


Later on, Scott would update the post, saying:


However, Ultimate Custom Night became such a big project that Scott later decided to make it its own game. and the "Endless Pizzeria" mode has yet to make any known progress if started at all.

The animatronic roster of Ultimate Custom Night changed quite a bit during development, with the major changes including:

• Changing number of animatronics to 50 from 40.
• Removing Adventure Endo-01 and Candy Cadet as playable characters.
• Adding Withered Chica, Withered Bonnie, Phantom Mangle, Phantom Freddy, Phantom Balloon Boy, Nightmare Bonnie, Nightmare, Nightmarionne, Nightmare Balloon Boy, Old Man Consequences, Funtime Foxy, Helpy, Nedd Bear, Orville Elephant, and Molten Freddy all as playable characters
• Merging Nightmare Freddy and Freddles into one slot
• Merging Bucket Bob, No. 1 Crate, and Mr. Can-Do into one slot and renaming them to "Trash and the Gang"

Putting Old Man Consequences on AI level 1 and pressing play would require the player to wait for the game to load and then wait for Old Man Consequences to show up to catch his fish. That would make a secret that was initially only seen in FNaF World appear, putting the player in a red world with Old Man Consequences sitting by a pond. Old Man Consequences would go on to say:


The player would then proceed to submerge themselves in the red pond, which would cause the game to crash.

YouTuber The Game Theorists held a charity livestream in 2020 for St. Jude Children's Research Hospital. Crowd Control, an interactive gaming app that lets streamers produce interactive, monetizable content with their community, created a mod for Ultimate Custom Night that let viewers of The Game Theorists' stream pay money to have events happen on screen or in-game. At the end of that segment, MatPat stated that this version of the game would become available to the public for other streamers to use, but it was never released.

Twisted Wolf (a character from the Five Nights at Freddy's novel trilogy) is seen on a poster in the left hall.