The Prison Costume is a restricted costume that was available as a Referral System & 2011 Facebook Contest prize. You can turn your pet into a Prison one if you do the following: getting caught Grave Robbing; overusing Illegal Concoctions; refusing to pay the electricity bill at the Power Station; and getting a job as a Thief or a Hacker. Putting this costume on your pet will make it turn into a prison convict. Prison pets are grey with black and white stripes (hat and/or mask may be included), a ball and chain, some scars, orange-yellow or blue eyes (Eyru, Limax, and Raulf are exceptions), and may look sad, mischievous, or angry.
Ball of Prison Yarn
Unlike the Prison Costume, you can get a Prison minipet by wrapping them in a Ball of Prison Yarn. It is obtainable from the City of Marada Goals.