All puppies and dogs act silly and goofy at times and yes, it can be quite entertaining. We do however have to determine when behaviors have crossed over from being funny to being a problem. A perfect example is the puppy or dog who barks at their reflection in a mirror or window, this is setting the stage for them to become reactive when they see other dogs. It seems so innocent when they do it the first time, everyone laughs as Fido goes crazy, but your dog just learned to go nuts when they see another dog. If a dog is constantly eating everything in sight, they have a foreign body surgery in their future if you don't manage their environment better. I've had clients brag about the things their dog could ingest, but trust me, you'll feel horrible when your dog suffers a bowel obstruction or worse, dies from eating something like a sock or some other choke hazard. Behavior problems can develop quickly and practice makes perfect, so the more your dog practices undesirable behavior the more you will see it rearing it's ugly head.
When should you intervene? I redirect any behavior that I feel encourages negative or unhealthy behaviors for my dog. The occasional chasing of the tail is ok, but after a few seconds I redirect the dog to do something else. If I am not able to redirect the dog, that is a clear indication that this is not an appropriate activity or behavior for my dog.
I once observed a Golden Retriever who loved to shadow chase in the shallow waters of the lake where his family lived. He would spend hours pacing back and forth chasing light shadows. It seemed funny at first and everyone joked about his 'fishing', but he developed a serious yeast infection on his paws from his hours of being in the water. His family tried to no avail to interrupt this behavior but he was almost mesmerized, unable to come out of what they described as a 'trance'. At first glance the owners primary concern was treating the yeast infection, but truth be told, they needed to address the shadow chasing to keep him out of the water. He was evaluated and placed on medication to control the compulsive behavior which kept him out of the water and allowed the infection to resolve.
If your puppy or dog is exhibiting a repetitive behavior pattern that you are not able to interrupt or redirect, it is advisable to consult with your Veterinarian and/or Certified Behavior Consultant. Dogs can suffer from OCD, a full assessment is warranted to make a diagnosis.
Lets not be entertained at the expense of our dogs physical or mental health.