Opossums on their mothers back at a game reserve in Central Minnesota, USA, on September 2, 2013. (Photo by Caters News Agency)

Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

A mouse rides on the back of a frog in floodwaters in the northern Indian city Lucknow June 30, 2006. (Photo by Pawan Kumar/Reuters)

A tiger is painted on the backs of three models at the Three Lanes and Seven Alleys on January 3, 2012 in Fuzhou, China. (Photo by ChinaFotoPress/ChinaFotoPress)

Birds sit on the back of a zebra in the Nairobi National Park, near Nairobi, Kenya, November 21, 2018. (Photo by Baz Ratner/Reuters)

Steve Shirts, aka “Strike Pony”, left, gets a hug from Amber Snyder, aka “Ditsy Dots” in Baltimore, MD on July 8, 2016. Both are from Suburban Chicago. BronyCon is the world's largest My Pretty Pony convention. Featuring cosplay and fan events, the annual convention was held at the Baltimore Convention Center. (Photo by Andre Chung/The Washington Post)

A picture released by the North Korean Central News Agency (KCNA) shows Kim Jong-un convening an urgent operation meeting at 0:30 am on March 29, 2013 at an undisclosed location, in which he ordered strategic rocket forces to be on standby to strike US and South Korean targets at any time. (Photo by KCNA via EPA)

1974: American boxer Muhammad Ali, formerly Cassius Clay, strikes an aggressive pose at a press conference on November 29, 1974. (Photo by Harry Dempster/Express/Getty Images); American actor Will Smith at the Royal Premiere of the film Ali in London on December 11, 2001. Smith starred as Muhammad Ali in the film. (Photo by Dave Hogan/Getty Images)