Robot couple Xiaolan (L) and Xiaotao carry trays of food at a restaurant in Jinhua, Zhejiang province, China, May 18, 2015. The restaurant, which opened on Monday, has two robots delivering food for customers. The robots were designed as a couple, Xiaolan and Xiaotao, according to local media. (Photo by Reuters/Stringer)

A dog wears “The Flash” costume for a carnival pet parade in Rio de Janeiro, Brazil, Sunday, January 31, 2016. People dressed their pets up for the annual block parade held near Copacabana beach. (Photo by Leo Correa/AP Photo)

Participants celebrate during the “Chupinazo” (start rocket) to mark the kickoff at noon sharp of the San Fermin Festival, in front of the Town Hall of Pamplona, northern Spain, on July 6, 2018. (Photo by Jaime Reina/AFP Photo)

A picture taken on August 7, 2017 shows a Snow Leopard (Panthera uncia) at the NABU center (Nature and Biodiversity Conservation Union), a German organization that aims at reintroducing the panther and fighting against poaching, near the Issyk Kul lake, in the outskirts of Semenovka village, some 330 kilometers southeast of Bishkek, the capital of Kyrgyzstan. (Photo by Vyacheslav Oseledko/AFP Photo)

Qian Hao's imported Pekingese dog, Mixiu, runs in a park in Beijing, China, February 8, 2018. (Photo by Thomas Peter/Reuters)

In this Saturday, March 3, 2018, photo, a contestant gets ready to throw a hatchet at a wooden bull's-eye at the Kick Axe Throwing venue in the Brooklyn borough of New York. Kick Axe Throwing is the first bar in New York City to pick up on a nationwide trend of ax throwing, a growing sport that some enthusiasts hope will take off the way bowling did in the last century. (Photo by Mary Altaffer/AP Photo)

A man sits waiting for a train on the London Underground in 1890, when the platform floors were still made from wooden floorboards. (Photo by Hi-Story/Alamy Stock Photo)

Two Bunny Girls from the Playboy Club and two Penthouse Pets from the Penthouse Club prepare to take part in the annual Good Friday waiters and waitresses race in Battersea Festival Gardens, London, 28th March 1972. (Photo by Ian Showell/Keystone/Hulton Archive/Getty Images)