His not-so-tiny offspring are being trained as guard dogs, and could be worth as much as $100,000 (£81,762.81) each.

The dogs become hugely valuable if they manage to complete owner Marlon Grennan's training school to become security dogs in New Hampshire.

The 28-year-old is currently focusing his attentions on training Kobe, one of Hulk's puppies.

Kobe is one of a litter of eight puppies fathered by Hulk, the "gentle giant".

Mr Grennan said: "My reputation is built on how I breed and train my dogs. I'm looking for the next Hulk, the star of the future. And this dog is the star of the future.

"Hulk is the most famous dog that I have but I am always looking for the next big thing, so I've got to keep marching forward and I think we have something here.

"Kobe is a wonderful dog, his father is the Hulk. He's got great energy, great balance."

Kobe used to be shy to bite, but now he can attack and release on command, seeing off would-be assailants.

Mr Grennan's business, Dark Dynasty K9s, supplies dogs to high-profile celebrities and billionaires as well as law enforcement around the world. 

He said: "To me Kobe is absolutely priceless, I have no intentions of selling him. I absolutely want to make him the superstar that I know he can be.

"But if I wanted to turn around and sell him tomorrow, I have already been offered $40,000 multiple times for him untrained based upon who he is and where he comes from.

"Kobe as a fully-trained dog, I would easily get $100,000."

Source:telegraph.co.uk