The personality question screen
Every Mii has a different personality. The personality of a Mii is determined by a quiz when the character is created. These are sliders for the following criteria: Movement, Speech, Expressiveness, Attitude, and if the Mii is overall quirky or normal.
There are four personality categories, and each category has 4 sub-categories, making 16 personality categories in total. A Mii always falls into two of those categories. And if another Mii greets a Mii with the same personality they could be friends!
The Mii's starting out room and pose are affected by what personality they are. When a child is ready to move into the apartment their personality will determine what starting clothes they get as well.
EU/AU have different names for the different types, but the interaction of Mis will all be the same.
Different Personality Types
Personality/chart
Interaction
Personalities play a role in interaction with other Miis. The different personalities of each Mii will determine how they act, who they get along or do not get along with, and who they will have a successful relationship with.