We started receiving the a photograph of a woman and a man leading a horse and a large dog through a park-like area), without any accompanying explanation, in March 2007. A few weeks later, someone added text identifying the dog as "Hercules, the World's Biggest Dog":
World's Biggest Dog, World's Heaviest Dog
Hercules: The World's Biggest Dog Ever According to Guinness World Records
Hercules was recently awarded the honorable distinction of Worlds Biggest Dog by Guinness World Records. Hercules is an English Mastiff and whas a 38 inch neck and weighs 282 pounds.
With "paws the size of softballs" (reports the Boston Herald), the three-year-old monster is far larger and heavier than his breed's standard 200lb. limit. Hercules owner Mr. Flynn says that Hercules weight is natural and not induced by a bizarre diet: "I fed him normal food and he just grew"... and grew. and grew. and grew.
This information was accurate (in the sense that an English mastiff named Hercules owned by a Massachusetts man was once recognized as the world's heaviest dog), but it didn't have any connection to the dog shown in the image displayed above, which clearly did not match a newspaper photograph of the real Hercules (and his owner):
(We note that the term "biggest dog" is somewhat ambiguous and is used here to mean "heaviest dog" rather than "tallest dog." Guinness currently assigns the latter title to Zeus, a Great Dane who measured 44 in. and passed away in 2014.)
An English mastiff named Kell, described as "weighing 21 stone (294 lbs.), taller than a Shetland pony, and more than six feet long," was previously described as the "world's heaviest dog," but it's unclear whether she was still alive at the time the "Hercules" photograph began circulating. (Different newspaper articles from 2001 referred to her as both living and dead, and we could find nothing but brief, indefinite mentions of her after early 2002. If she were still alive, why she ceded the "world's heaviest dog" title to Hercules would be puzzling, because news accounts generally listed her as being slightly heavier than Hercules.)
Also, the dog pictured above looks to be a Neapolitan mastiff rather than an English mastiff. If so, the canine would appear to be either a digital manipulation or a freakishly large example of its breed, because adult Neapolitan mastiffs typically reach a height of 24-31 inches at the shoulder. (Contrast, for example, the above image with other photographs demonstrating the size of Neapolitan mastiffs relative to people. Adult Neapolitan mastiffs typically reach a height of 24-31 inches at the shoulder.)
Another image shows the same scene from the rear: