Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)

Women perform a pole dancing routine during the national day celebration of “Urban Pole” dance along a street in Monterrey, Mexico, on June 9, 2013. (Photo by Daniel Becerril/Reuters)

People take photos as an Ariane 5 space rocket with a payload of four Galileo satellites lifts off from ESA's European Spaceport in Kourou, French Guiana, on November 17, 2016. Ariane 5 successfully launched on November 17 four satellites which will be part of the Galileo global satellite navigation system. (Photo by Jody Amiet/AFP Photo)

A girl walks past campaign posters for long-time President Yoweri Museveni, as well as for local members of Parliament, on a street in Kampala, Uganda Wednesday, February 17, 2016. On the eve of presidential elections, a heavy police and military presence could be seen in the capital Kampala. (Photo by Ben Curtis/AP Photo)

Visitors dressed in superhero costumes attend the Paris Comics Expo at the Parc Floral in Paris, France, April 15, 2016. (Photo by Charles Platiau/Reuters)

People slide down a 1,082 feet (330 metre) long inflatable water slide in Hong Kong, China August 22, 2015. (Photo by Tyrone Siu/Reuters)

Dancers wearing masks and kimonos perform in the streets at the “Super Yosakoi 2015” dance festival in Tokyo on August 30, 2015. One hundred dance teams with some 5,500 people participated in the two-day summer festival event. (Photo by Yoshikazu Tsuno/AFP Photo)

Contestants of a tattoo competition pose for photographs at the China TATTOO convention in Nanning, Guangxi Zhuang Autonomous Region, China, October 24, 2015. The annual convention was held in Nanning from October 23 to 25 this year. (Photo by Reuters/Stringer)