A stock character is typically a character that is recognizable due to their stereotypical or archetypal personality. They are often cliche in nature and may be ridiculed or parodied by others. A flat character is simply a character that does not develop throughout the story. They are often very simple in nature. A round character is the opposite of a flat character. They are well developed, realistic, and complicated. They develop as the story progresses. Hope this helps.
