Yeah, those places you've put in blue were just errors. As I was using Oil Brush I had to use an Art layer, which means not being able to erase anything without turning it into a raster, and I didn't want to do that until I at least had the basic sketch done. XD I must have uploaded an earlier save of it for it not to have the paw lines.
And no, a mouse. My partner has a tablet but I can't get the hang of it. Every time I put the pen down the mouse shoots off to an unwanted part of the picture, even if I align the mouse very carefully before I put the pen down.