As intelligent as pups are, they sadly are not among the very few species in the animal kingdom that is capable of passing the self-recognition test. In other words, pups are unable to recognise that the other pup in the mirror is just their own image reflected, and not some other strange pup.
With how many reflective surfaces can be found in a modern house, this can obviously lead to some funny situations where the pup tries to figure out how to approach the other nonexistent pup! In this particular case, this pup has spotted his own reflection in the black surface of a television screen that has been turned off.
Incensed at this stranger daring to wander into his home, he starts barking at it. You can see how he eyes his reflection and shifts his stance, trying to psyche out and declare dominance over his territory with his body language!
Feature Image Source: ABargainBeautifulLife