To make an easy mummy costume for your dog, wrap its legs, torso and head in either an ACE bandage or in cotton gauze. Alternatively use a white hoodie that has been decorated with white gauze. Don't forget to leave plenty of space so your dog can urinate or defecate.
To turn your dog into a skeleton, first acquire a child's black hoodie and white fabric paint or white felt fabric in bone shapes. Glue the bone shapes to the back of the hoodie in a skeleton pattern or, if using fabric paint, draw the skeleton on the hoodie. If you have a smaller dog, wrap the bottom corners of the jacket around the dog's back legs, and stitch in place. For a larger dog cut the crotch out of bike shorts, decorate with bones as necessary, and put them on your dog.
Turn your dog into a ghost by putting a white sheet over its head and making markings at the feet, eyes, nose and ears. Remove the sheet, and cut the excess fabric at the bottom. Cut holes for the eyes, nose and ears. Attach a length of elastic inside the fabric in such a way that it can hold the sheet around the dog's neck and prevent shifting. Do not cut the sheet while your dog is wearing it.