Sissel

Sissel is the protaganist of the video game Ghost Trick: Phantom Detective, where he appears as a ghost who attempts to discover the mystery of who he is and why he was killed. He has the powers of the dead, which he uses to revert people's deaths. The end of the game reveals he is actually the pet cat of Yomiel, the man whom's body he mistook for his own throughout the majority of the game. Because the first body he saw when he woke up was a human's he assumed he was a human himself, and so assumed his lack of basic understanding, his inability to read English, and the fact he was having such a hard time remember who he was, was due to memory loss after becoming a ghost. In act fact, these things were all down to the fact he's a cat.

At the end of the game, time is completely rewritten so that the events of the game never happened however Sissel still remembers it. The Temsik fragmant which had pierced through Yomiel in the first version of events ended up piercing through him during the new version. Due to this, Sissel gained immortality, never being able to age, but also maintained his ghostly abilities. In this new timeline he becomes the pet cat of Jowd and Kamila.

Trivia
The twist as to Sissel's real nature is foreshadowed many times throughout the game.
 * When discussing Cabanala's "spotless white coat", Sissel mentions that if it was him he'd just have a black coat that doesn't show the stains.
 * He recalls that he used to love crawling into small spaces when he was alive.
 * When one of the prisoners is playing his jailer, Sissel wonders if it's a way for the prisoner to express things such as "I'm hungry".
 * Ray tells Sissel at the start of the game, "when the man pulls the trigger, the girl dies". What seems like a captain obvious line gains revelance when you realize Sissel would need that information, since he wouldn't know what a gun is.
 * The amoun of lives Sissel saves is 9. A cat is a traditionally said to have 9 lives.
 * A number of the puzzles in the game involve having to harm a mouse.