It's just that according to the story of A Huge Tragedy With The Deaths Of Animatronics in the first part, in a restaurant with animatronics, they wanted to buy new animatronics so that they could be transferred to the next pizzeria, so it was decided to make prototypes. However, due to an incident in which families were killed, the new main antagonist planned, which caused the prototypes to be unfinished. Among them was the Unfinished Freddy, who was more used than the rest, but he didn't have a soul. However, the killer decided to put a program in it so that it would attack people, and the killer also controlled it through controls, as with the Nameless animatronic.

In addition, the Unfinished Freddy was left in the office to quickly attack the main character of the first part, but he constantly resisted. However, the main character broke this Freddy, which made him unusable. In the third part, we also used his mask to hide from the animatronics...

He also has no fur, so he looks grayish...