The phrase "chasing the dog" can refer to different scenarios depending on context:

• In a viral video context, a man was chasing his dog named Fenton, who was running after a herd of deer across a field. This video became popular online, showing the man yelling "Fenton!" while trying to catch his dog

• In everyday situations, people often chase their dogs playfully, such as a person running after their dog in a park for exercise or fun

• There are also fictional references like the "Chasing Dogs," a trio of dogs from the TV series Go, Dog. Go!

• Additionally, in animal behavior, dogs sometimes chase their own tails compulsively, which is a different kind of "chasing" related to canine compulsive disorder rather than chasing by a person

If your question refers specifically to who was chasing a dog in a notable or viral instance, it was a man chasing his dog named Fenton as the dog ran after deer

. Otherwise, it could be any dog owner or person playing with or trying to catch a dog