Fossilized Oswald is a unofficial antagonist in Abandoned Discovery island. As you can tell from his name; he is a fossilized 'Oswald the Lucky Rabbit' suit, with many broken features.
He appears to look similar to Dark Oswald, however he's missing his left foot, a left ear, seems to look all dusty around (like the abandoned suits), and has is missing arms.
On Night 4, he becomes active around 12 AM in Character Prep 2. He will then spawn to the Lounge, and then the Office.
When he's in the office, shut off a camera or hide under the desk, or just turn off the power. Otherwise you will die to him.
The Fossilized Oswald uses a 'Epic Mickey 2: The Power of Two' model, rather than the 'Epic Mickey 1' models. (which was used for the original Oswalds)
In his jumpscare he has a orange glow to him before the last frame.
The Oswald was "possibly" discovered outside Discovery Island and beneath the ocean. When he was discovered, he was put inside Discovery Island in Character Prep 2. (mostly for props and restoration)
Fossilized Oswald is possessed by a person who rotted inside him. (nothing but bone dust)