Visitors at the National Zoo check out a parrotfish made from found waste from the ocean in Washington, DC on May 23, 2016. The artwork can be seen at the National Zoo until September 5th. (Photo by Keith Lane/The Washington Post)

An Orthodox priest conducts a blessing in front of the Soyuz TMA-20M for the next International Space Station (ISS) crew, comprised of Jeff Williams of the U.S. and Oleg Skriprochka and Alexey Ovchinin of Russia, at the launchpad at the Baikonur cosmodrome, Kazakhstan, March 17, 2016, ahead of its launch scheduled on March 19. (Photo by Shamil Zhumatov/Reuters)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

A woman dressed up as a zombie takes part in a zombie walk in the Gaslamp Quarter during the Comic Con International convention in San Diego, California July 13, 2012. (Photo by Mario Anzuoni/Reuters)

“A dirty thunderstorm (also, Volcanic lightning) is a weather phenomenon that occurs when lightning is produced in a volcanic plume. Dirty thunderstorms have been reported in Chile above the Chaiten Volcano, above Alaska's Mount Augustine volcano, and Iceland's Eyjafjallajökull volcano”.

Photo: A cloud of ash pours from Puyehue volcano in southern Chile, at sunset on June 5, 2011. (Claudio Santana/AFP)

In April 2011 last factory in the world on manufacture of typewriters was closed. The epoch of typewriters has ended...

Photo: A model of a commercial typewriter from 1867. (Photo by Topical Press Agency/Getty Images). June 1923

Marianne Brauns jumping a breakwater on the beach, wearing a structured blue swimsuit with white trim. (Photo by Carl Sutton/Hulton Archive/Getty Images). Circa 1950

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)