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.
Subject 3 also gives Professor Layton and Luke a few puzzles during their time investigating north Future London. The first puzzle he gives is "Rabbit Hops". The other is "Five Swimmers". He also gives, to Luke, a new Toy Car track.
- Subject 3 identifies the Parrot Luke owns as Subject 1, one of the animals tested before him, however, Subject 2 is never mentioned.
- Subject 3 is seen later behind a bush as the Parrot waves goodbye to Luke and Professor Layton, suggesting that he survived the explosion.
- In the tenth episode of Layton Mystery Detective Agency: Kat's Mystery-Solving Files, Subject 3 is seen as one of the accessories on Marina's handbag.
- His horrifying experimentation backstory and bad attitude resulting from it, is similar to Marvel Comics hero 's.