Preheat the oven to 375 degrees F. Unwrap the crescent dough and lay flat on a cutting board. Cut at the perforations to create 4 even rectangles. Press the other perforations to seal.
With a sharp knife, cut each rectangle lengthwise into 10 strips, making a total of 40 strips of dough.
Take one hot dog at a time and make two slits along the sides for the mummy’s arms. Make a slit at the bottom for the mummy’s legs.
Wrap strips of dough around the individual arms and legs and then around the body of each hotdog, leaving small space for where the mummy’s face will be.
Place the mummies on a large (ungreased) baking sheet and lightly spray the dough with cooking spray.
Bake for 12-15 minutes or until the dough is light golden brown. Pour some mustard in a plastic bag and snip off the tip of the bag with scissors. Pipe "eyes" on the mummies.
Enjoy the mummy dogs with extra mustard and ketchup if desired.