Jealousy the Endoskeleton is a minor non-antagonist character in The Rewritten Nights of Freddy's
His appearance his that of a withered and entirely bare ''02'' endoskeleton missing an arm, foot and the front portion of his face with upper jaw.
Once a night begins Jealousy will make his way to the office and once inside will stare at Jake for a short period of time.
If you were to not wear the mask Jealousy would simply then leave the office till the next time he would appear, though if you to wear the mask he would then steal it from you and place it on his head where he would ignore the you for the nest of the night.
This is because like his name suggests, Jealousy was an endoskeleton that never got a chance to be used when he was fully functional and as such became jealous that almost every other animatronic has a suit for why he steals the Jakes mask.
Fun fact, while having nothing related to the lore, the model used for Jealousy is of Withered Bonnie, explaining the missing face and wires coming out of his arm.