My very first Sonic custom sprite
Ok, well, that's a start. I can see the changes you made for sure, one thing to be careful of is making things too square. Try to made the quills rounder first.
So is this sprite part of a running animation?
No, I made this sprite all by myself, trying to make the same pose as the sonic advance 3 one. But I took the foot from the running sprite to look like hes sorta jiggling his leg. and one hand on his hip.