Another large category of supporting roles are what are generically called types or stock characters . This refers to the age-old dramatic practice of reducing complex human beings down to simplified, almost cartoonish, caricatures. It is a shortcut used by dramatists to provide characters that are already familiar to an audience, thus saving the time normally required to explain what they are all about. Such characters have been around since the classic comedies of the Greeks and Romans, and while their specific names have changed, they remain amazingly similar. Bad guys in general are sometimes referred to as heavies.
Stock characters can be heroic, ordinary, or villainous.
When stock characters make an appearance the audience already knows pretty much who they are and what to expect from them. The time saved by this device can then be devoted to more carefully developing central characters. Casting directors and agents use such stock types to categorize both the roles and the actors who can readily play them. Finally there are the smallest roles which range from the fairly important cameo, to the least significant extra. A cameo role is a very small part that is played by a famous actor.