Prototype has the appearance similar to that of a endoskeleton, possessing lanky, non-moving arms, ears, yellow-green eyes, robotic claws, and a dapper hat and bow-tie. Prototype shakes back and forth minorly. Its face closely resembles Freddy's with triangular-shaped teeth.
Basic "hook" attack
Deals medium damage to a single party member.
Summons an amount of melted cheese that deals damage over time (puts 5 globs instead of 3).
According to the first trailer and the image on the IndieDB game page, the design of Prototype was changed before release, as well as the idle animation.
Prototype's original design had the bow-tie and dapper hat colored in purple, instead of black, the dark purple parts of Prototype's torso were orange. Prototype also appeared to have red eyes and claws, while currently, the aforementioned parts of Prototype's are colored green and light purple.
The original bow-tie and dapper hat color made Prototype show resemblance to Nightmare Fredbear in both FNaF World and the core game (Five Nights at Freddy's 4)
This ironically means that there is a prototype of Prototype.
Prototype's original idle animation had arms that were able to bend rather than droop downwards, and its bow-tie was originally going to spin. Prototype also was possibly originally to be encountered in Fazbear Hills and Dusting Fields.
However, this may just be because Fazbear Hills and Dusting Fields could have been the only areas to be finished at the given time of development of the game.