Here I also did the character sheet for the Rat.
I went for a more simple design with the rat as he is the "bad guy" in this film. The cat is more friendly and approachable than the rat.
We didn't want to go for a plain black or brow rat as rats are often associated with disease. So we went for a dull purple colour so that he looked a little more friendly than you normals bog standard rat.
Purple can be considered "artificial" and this ties in with the Rat attitude towards the Cat in the film, so this was a nice link.
I also based the rat off of a character from an anime (this is also where I got the inspiration for the film) called Fruits Basket, in which 13 members of a family turn into one of the 12 animals (plus the cat) when touched by members of the opposite sex. A boy in this anime, called Yuki, turned into the rat. Our rat is influenced by him. I like to think of it as a little homage to the anime as it was where I first heard the Cat and Rat story.