A dog dressed in a costume takes part in the Pet's Halloween Day parade at Abtao Park in San Isidro, Lima, October 31, 2016. (Photo by Guadalupe Pardo/Reuters)

In this November 17, 2014 photo, Pancho, a domesticated huitia, confronts a camera, in Bainoa, Cuba. With their rope-like, dark tails, long front teeth, and whiskers that appear to be vibrating, huitias look like giant rats. They measure nearly a foot long (about 30 centimeters), with the largest ones weighing in bigger than a small dog. (Photo by Ramon Espinosa/AP Photo)

A dog relaxes in an oxygen capsule “DOGS O2” at the Ownd Cafe on September 13, 2007 in Tokyo, Japan. The capsules come in a variety of sizes available for both dogs and cats for relaxation purposes. (Photo by Koichi Kamoshida/Getty Images)

German photographer Tobias Lang had a brilliant idea, he started photographing his friends and their pets and suddenly folks from all over the world where asking him to capture them too. Check out his Facebook page to see. Tobias is in the process of putting together a coffee table book of his impressive collection. Photo: Pet owner Isabel with her blind housecat, “Captain Jack”. (Photo by Tobias Lang)

“In anatomy, heterochromia refers to a difference in coloration, usually of the iris (but also of hair or skin). Although infrequently seen in humans, complete heterochromia is more frequently observed in other species, where it almost always involves one blue eye”. – Wikipedia (Photo by StooMathiesen)

South Korean special warfare command soldiers participate in winter military training exercise on January 11, 2012 in Pyeongchang-gun, South Korea. The South Korean troops train in temperatures below -20 degrees celsius to defend the country against any possible attacks from North Korea. (Photo by Chung Sung-Jun/Getty Images)

Rihanna arrives for the Stella McCartney Special Presentation at 13 North Audley Street during London Fashion Week Autumn/Winter 2012 on February 18, 2012 in London, England. (Photo by Samir Hussein/Getty Images)

A dog dives during a pet dog swimming contest at the Taoyuan Pet Center on July 31, 2005 in Chengdu of Sichuan Province, southwest China. Over 30 dogs have attended the match. According to state media, with the country's pet population growing fast, analysts predict that the market potential for the “pet economy” in China could reach a minimum of RMB 15 billion (about USD 1.85 billion). (Photo by China Photos/Getty Images)