Two site pets, so that means... PNG MASHTIME!!! (I actually love .png mashtime.. but only when it's 100% justified)
The undead was obviously used as a base on this one, with some gory color mixing onto the zombie. Looking back, they probably wanted the skullface and the bandages on the halloween one, but I didn't think of that then, and went for the zombie edit instead.
The old circle was cut out and replaced with the skull, which I desaturated the green off of to match, and added in the skull earrings too, on their own separate layer.
Mixing the colors made it look like rotten meat... and well.. you DID breed a zombie. I played with several color layers to make it in the sickening rotting coloration you see here, and made sure the wisps stayed in tact.
Somehow I included the foot fog from the halloween parent (and made it a farty gross color too). I probably cropped it mostly out and put it behind everything at a low opacity.