General

Stardew Valley is another game where there are several mods which make certain NPCs fat. Currently they are static (so the NPCs become fat from the beginning, not gain weight), but it's theoretically possible to make a mod which makes NPCs to dynamically gain weight. (I checked the code, it's possible)

If no one else makes it, and I'll find enough time for it, maybe I'll code such a mod...

I don't think it's weird. I've had that desire/wish too. Seems like a natural desire to want to see that portrayed in a game. Since many games have slender Caucasian characters, sometimes I wonder if other ethnicities feel left out or would enjoy seeing their demographic represented, just like I'd like to see fat people or weight gain represented.

I remember having fat characters in Saints Row 2 and GTA San Andreas