People use a board to travel on a flooded street after heavy rainfall in Baghdad, Iraq, October 31 2015. (Photo by Ahmed Saad/Reuters)

Women dressed as nuns pose for pictures during Halloween celebrations in the Shibuya district in Tokyo, Japan October 31, 2015. (Photo by Thomas Peter/Reuters)

Women in costumes walk as they participate in Halloween celebrations in the downtown of Seoul, South Korea, October 31, 2015. (Photo by Kim Hong-Ji/Reuters)

Bonobo apes, primates unique to Congo and humankind's closest relative, groom one another at a sanctuary just outside the capital Kinshasa, Congo on October 31, 2006. (Photo by Finbarr O'Reilly/Reuters)

The 2016 Greenwich Village Halloween parade, October 31, 2016 in the Manhattan borough of New York City. (Photo by Anthony Causi)

A cosplayer poses for photographs at the 2015 Comic Fiesta event in Kuala Lumpur, Malaysia, October 31, 2015. (Photo by Olivia Harris/Reuters)

A man dressed up as a "Catrin", a Mexican character also known as "The Elegant Death", is pictured during a Catrinas parade in Mexico City October 31, 2015. (Photo by Carlos Jasso/Reuters)

A remote-controlled plane in the form of a witch flies over a neighborhood as the sun sets during Halloween in Encinitas, California, U.S. October 31, 2016. (Photo by Mike Blake/Reuters)