Jack

Jack is Douglas's former roommate and friend. It is currently unknown for how long they were roommates. It appears they still are friends and in good contact. Jack carries himself with confidence and integrity to the law, as he is not afraid to call out Douglas for having murdered Arvel the Swift.

Jack's heart.
Jack's heart has the ability to grow. At the time of writing it is unknown how large Jack's heart is, and whether he can force his heart to grow at will. During a video of Jack and Doug playing Mario 64, Jack's heart grew three sizes, and the Power of Friendship activated. If the Power of Friendship was activated by the initial heart-growing is to this day still unknown.

The Follower Trials
Jack contributed massively to both Fondle's case and Lydia's case, in which both were convicted.