Peel the top portion the pear, removing the stem if still in place.  This will serve as the "head" of the porcupine.

Using toothpicks, pierce each grape into the larger portion of the pear to resemble the "back side" of the porcupine, leaving the smaller portion of the pear as the "head."

Place a black olive over the top of the pear for the nose of porcupine.  Finish off by piercing cranberries with toothpicks as the eyes of the porcupine.