Weight Classes are categories given to the characters on this wiki. They are used to describe the character's body size.
Thin characters are slim, and have flat bellies. They're at most, the average body weight of a creature their age. They are also likely to be energetic or athletic. They may be thin because of their athletic abilities, high metabolism, or even lack of food.
Chubby characters are slightly larger than Thin characters, and have rounder stomachs. They usually aren't ridiculed by their larger bodies (unlike Overweight or Obese characters). They aren't too lazy or gluttonous, most chubby characters have bigger bodies due to genetics (still there are some who do have big appetites).
Overweight characters have noticeably large stomachs, and are shown to have appetites to match (unless their size is just genetics). They are typically lazy and hungry, and are often annoyed when other people (namely 'thin' people) point out their size (sometimes claiming it false because they are "big boned").
Obese characters (as rare as they are) have enormous bodies, even at times, to the point of being immobile. They often stop at nothing to get food, while some may be lazy and weak, others and learned how to use their size to their advantage.