Hit the fabric store and get a length of fake fur. A yard should do. Simple drape it over you and cut a hole where your head should poke out. Lace up the sides by poking holes in the fabric and threading with a neutral color of ribbon or leather lacing.
Use facial mud mask cream to smear on your face around the cheeks. Don't put any on your brow or forehead because it may get in your eyes as you sweat.
Find a fake bone to roll in your hair. Start at the front and roll the bone in. Hide a hair clip where the bone meets your head to secure. Some leaves wouldn't hurt...you can also use mud from a facial mud mask to dirty up your hair.
If you must, wear sandals.