There is a total of 10 different models of the Fighting Polygon Team. Each represents each of the 12 characters with similar fighting techniques. Only one Polygon Fighter represents three characters at the same time which is Mario, Luigi and Ness.
Ness refers to his magic attacks as "PK" attacks. This is supposed to be "PSI." (The Earthbound games use the term PSI to refer to magic, though an early beta version of the game used PK, and this is probably what caused the error.)