People who are animal lovers tend to fall for every creature they see. But no matter how cute every animal is in its own way, it's no secret that dogs are still man's (and woman's) best friend. The fuzzy creatures are smart and loyal, capable of forming strong bonds with their owners like no other species. So how would you react if you suddenly realized that your dog is no longer the same dog that you brought home?

Su Yun recently confronted this question when the so-called Tibetan Mastiff puppy she adopted didn't turn out as she expected. The Chinese native had heard of huge dogs, but this was something extraordinary. Her beloved pup grew up to be almost 3-feet-tall and weighed in at 250 pounds in just two years' time! The remarkable story even captured the attention of National Geographic, who published an article explaining the science behind the crazy phenomenon.

Continue reading below to find out exactly what was going on with Sue's massive dog--the truth might surprise you.