Subject 3 is a rabbit appearing in Professor Layton and the Unwound Future. He was one of the test subjects in Dimitri's lab, which gave him the ability to walk on two legs, as well as being able to speak. Subject 3's ability to speak has also given him quite the attitude. He is quite rude to Hershel Layton and Luke during the beginning of their adventures in Future London. Later on in the game he tells them of his sad story about how the scientists did tests on him. His name, Subject 3, is what the scientists in Dimitri's lab called him as well, so he decided to keep it.
When he was a baby rabbit, Subject 3 was picked for an experiment by Dimitri, possibly for the time travel machine. Separated from his family, Subject 3 was scared and angry. During one of the experiments, he was given the unusual ability to talk and in another walk and behave in a human way. At an unknown point he was either released or escaped the clutches of Dimitri. He came to the Thames river where he eventually met Layton and Luke.