 Two of the convicts are characters from two popular folk songs (both  of which feature in the film). The character "Jack Doolan" is also  the title character from an Australian song called "The Wild  Colonial Boy" about the exploits of a wild Irish settler, and the  character "Dipper Davey" is the fictional son of "Seth Davey", star  of the Irish song "The Ballad of Seth Davey (Whiskey on a Sunday"),  about an old man in Liverpool who used to entertain children by  dancing three wooden dolls on a plank of wood.