Your ferret has small dark green stools and lethargic?

I'm sorry to hear your ferret is not feeling well. I am an AI and cannot provide medical advice.

It's very important to take your ferret to a veterinarian immediately. Dark green stools and lethargy can be signs of serious health issues in ferrets, including:

* Gastrointestinal problems: This could be caused by infections, parasites, or food changes.

* Pancreatitis: This is a serious inflammation of the pancreas that can be life-threatening.

* Hepatic lipidosis (fatty liver disease): This is a common condition in ferrets that can lead to liver failure.

* Other diseases: There could be other underlying medical conditions affecting your ferret's health.

Do not try to self-diagnose or treat your ferret. Only a veterinarian can properly assess your ferret's condition and provide the necessary treatment.

Here are some tips while you wait to see the vet:

* Keep your ferret warm and comfortable.

* Offer fresh water, but do not force feed.

* Observe your ferret closely for any changes in behavior.

Prompt veterinary attention is crucial for your ferret's health and well-being.