So… a few days ago I got the idea of respriting Terraria’s enemies into fat monster girls and after a bit of research I stumbled upon the 1.4 texture pack support update. I’ve played a bit with the small slime sprite (NPC_1), made a texture pack format and put the sprite in and… 
So, technically, we could make a Terraria fat mod by using the texture packs and through a texture pack we can make everything fat from the enemies to the town NPC to even the PC it’s self.
However, by using a texture pack to resprite Terraria’s sprites we gonna meet some limitations and those are the ones I found out so far:
-Some enemies (such as the slime I sprited in the picture above) don’t turn left and right so, If you sprite one of those enemies facing sideways they gonna be stuck facing the side you sprited it .
-Like Stardew Valley, By using this method we might gonna have to concern about the sprites limit. At best, If the texture pack sprite pass that limit it simply works but the hitbox wouldn’t be accurate. At worst, if the texture pack sprite pass that limit it might glitch up or even worst, crash the game. The good part is that this limit varies from sprite to sprite and so, some sprites might have a larger limit to work with (such as bosses).
And so, I hope I inspired you with this post, myself I’m gonna attempt to make some more of these sprites as much as the time allows me. Personally I see a lot of potential for a fat Terraria with the method and I hope to see the community’s input on this idea.
With that said, If you have any questions or thoughts about this Idea I’d be more than happy to hear and answer them!