The Prisoners are the main characters from Jailbreak. There are technically three Prisoners but really they are all pretty much the same dude. Over the course of the game your awareness passes back and forth between them, and at one point splits into two distinct paths.
The First Guy Edit
You start as this Prisoner when first beginning Jailbreak. He is in his cell with absolutely nothing, useful or otherwise. Over the course of the game this Prisoner murders a Dungeon Master, makes himself a suit of armor out of some pumpkins, and gets harpooned.
The Other Guy Edit
This Prisoner starts out in between two of the prison buildings, rather than locked in a cell. Over the course of the game he gets peed on, vomited on, and builds a robot.
The Drill Guy Edit
The last Prisoner starts in the cell above the first guy. In his room is a giant drill which he has never thought to use as a tool for escape. He manages to snap his own neck after his head gets stuck in a hole in the floor. His blood trickles down into The First Guy's room.
The First Guy, Again Edit
After getting a Game Over, Jailbreak starts over with the first guy again. This time he manages to escape fairly easily after beseeching the help of an elf. His eventual fate is unknown, though he appeared to have been in a steady downward spiral into madness after partnering with a pony (which he received from the elf) and stealing children from a schoolbus.