Mario Enemies in new style

[Gors]

How do make them ?
I mean what color paletes do you use or what kind of bodies you make them ?
I'm really interested in this, they look very good, speacilly Petey Piranha !
One of my most favorite characters in the mario sagas.

Custom colors, custom bodies. I'm pretty sure it's his style.

EDIT: I checked your sprites, and I have some criticisms to give. Your shade of yellow (Koopa's skin, for example) is too bright. And something isn't right about the giant Goomba... His face stays almost the same in the 3rd frame when it should be placed a bit more to the right (his left).