Oswald is a cranky person but can be nice once he starts warming up to you. Mess with his younger siblings, you will be living in HELL. He doesn't usually like people unless they help one of his brothers.
Oswald looks like both counterparts. He had a long sleeved jacket and detachable rabbit ears and a tail. He has Sans's pants, except they're blue, and has no gloves. He wears blue chucks.
Oswald was a star in his day. But one day, he fell down. He woke up in a new place, knowing what had happened. He soon found out that Mickey Sans had taken his place and he was furious. He left to WasteLand where he became the ruler for years.
The events of Epic Mickey 1:
Oswald lives in peace until his old owner, Chara Mintz, comes back for him and tortures him for a while. Mickey saves him and Oswald earns a heart along with everyone else from WasteLand.
The events of Epic Mickey 2:
Mickey fell down and Oswald almost went down with him until Sadys came and helped them. The brothers reunited.