The Deadly Rat

The deadly rat is a jet black, slimy, 2 ft long rat with glowing red eyes and sharp teeth that enters through the mouth and expands inside someone until they die and exits through the mouth.
The deadly rat also walks on its hind legs when it sees a target.

SOMEONE HELP! THE DEADLY RAT ENTERED DAVE AND DAVE IS EXPANDING! PLEASE HELP! NOBODY CAN SAVE DAVE! THE DEADLY RAT IS TOO MIGHTY AND FAST!