Meet the conditions to unlock new characters. They can be selected before the start of a game. Note that the requirements are your total blacksmith level; not the level you have reached in one game. Blacksmith is unlocked by default.

Character	How to unlock
Barbarian Smith	Blacksmith Level 05
Caribbean Smith	Blacksmith Level 18
Cook Smith	Blacksmith Level 22
Cosmonaut Smith	Blacksmith Level 21
Doctor Smith	Blacksmith Level 06
Eskimo Smith	Blacksmith Level 17
Footballer Smith	Blacksmith Level 12
Gaben Smith	Blacksmith Level 13
Ghost Smith	Blacksmith Level 02
Gold Smith	Blacksmith Level 23
Hockey Smith	Blacksmith Level 14
John Smith	Blacksmith Level 03
Ogre Smith	Blacksmith Level 07
Old School Smith	Blacksmith Level 08
Pirate Smith	Blacksmith Level 09
Robot Smith	Blacksmith Level 04
Rocky Smith	Blacksmith Level 16
Sailor Smith	Blacksmith Level 10
Scot Smith	Blacksmith Level 15
Sumo Smith	Blacksmith Level 11
Tasmanian Smith	Blacksmith Level 20
Viking Smith	Blacksmith Level 19