Terraria Community Forums

I don't know much about art, but why would it?

It's not about art.
It's about how file sizes are measured. .gif is a messy region apparently.

.gif = image with moving frames
.png = high quality image

As I recall, .png can do animations as well. Maybe that's the reason?

Well, a gif is an animation/multiple frames, while a png is just a single image/frame.

Copy pasting it in a new file seems to fix it.

Okay, I see.