A Guard Dog is an enemy in Crash Twinsanity that appears in the Academy of Evil levels. 
Green Gem 16-B


The behavior of the Guard Dog varies between levels;

In the Academy of Evil hub level, the dog will simply wander back and forth. It will do no harm to Crash unless he touches it.

In Classroom Chaos, however, three of these dogs and they will make a dash towards Crash if they notice him.