Preheat the oven to 425
Cut the crescent dough into strips that are around 1/8th of an inch wide. Don't worry about pressing together the seams before you do this, because the mummies look better when there are little ends of dough poking out.
For each sausage, take two strips of dough and flatten and stretch them out until the strips are at least 50% longer than they were originally. Wrap the strips around the sausage, one at a time, making sure to overlap the strips to create the "mummy" look. Use your finger to wedge a space near the top of the wrapped sausage for the mummy's "face".
Once all sausages are wrapped with dough, whisk the egg in a small bowl, and then brush each mummy with the egg. This step is optional, but it gives a nice, brown sheen to your mummies.
Bake at 425 for 16 minutes, serve warm.