You can view the actors and the characters they play in various ways.
This lists the actors, and the characters they have each played across all four seasons. This list is best if you want to compare differing roles an actor has peformed.
This lists each individual character from seasons one and two, and the actors who portrayed them. This is the list to use if you're looking for a specific character.
Lists the characters from season three, and the actors who played them.
Lists the characters from season four, and the actors who played them.