“When the plumbing gets tough, the tough get plumbing”
A Plumber is an occupation that exists in both the Earth and the Mushroom World. A plumber's job is to install and maintain piping and apparatuses connected with water transport and drainage systems, which occasionally includes work such as unclogging drains. On Mushroom World, a plumber's job seems to involve cleaning and maintaining various sewers and fixing Warp Pipes. The most notable plumbers in the Mario series are Mario and Luigi, and the main protagonists at that.
When the explorer Marco Polo went to China, he and his crew brought back many discoveries to Europe. One of these was the art of plumbing. Marco Polo's Plumbers learned plumbing in China and later introduced it to the city of Venice. Plumbing later spread through Europe and sewer systems became essential for modern towns throughout the world.
Hundreds of years later, the famous plumber Salvador Drainado founded the Brooklyn Plumbers Academy to spread plumbing to a younger generation. Many plumbers, including Mario and Luigi became plumbers here under the strict teachings of Sergeant Kooperman. Mario and Luigi became renowned for their abilities when they saved the president of the United States of America from a sewer flood. The president gave Mario the Golden Plumber's Helper and Luigi the Golden Wrench as thanks. The brothers later founded the Mario Brothers Plumbing business, where they continued their jobs, and received the Plumbers of the Year award by the Imperial Poobah of the Grand Order of Plumbers.
In the Mushroom World, there seems to be very few plumbers, which is odd since they have many sewers and Warp Pipes. Instead, the few plumbers are often seen as celebrities, with Mario being world-famous, Mighty Plumber having his own successful television show, and there even being a plumber who is a comic book hero, Dirk Drain-Head. One of the few times a plumber is requested is in Super Mario Adventures, where Mario and Luigi are called to Princess Peach's Castle in order to fix a sewage problem.
Plumbing isn't often a heavy focus of the Mario games and the Mario Bros. have only fixed sewers directly in two of them. In the game Mario Bros., Mario and Luigi cleaned the sewers of the foul monsters that infested them, and the two fixed the leaks in the Beanbean Castle Piping System in Mario & Luigi: Superstar Saga. Plumbing got a passing mention in Paper Mario, when Goombario said in Toad Town Tunnels, "Uh... I think this is a sewer. You know... the Toad Town sewer. Under Toad Town. What am I saying? You know! You're a plumber, after all!" In Luigi's Mansion: Dark Moon, more is made of Luigi's career as a plumber. A wrench and a plunger can be seen crossed over his fireplace, one mission is titled "A Job For A Plumber," and Professor E. Gadd says that if Luigi doesn't want to become a ghost hunter, he could always be a plumber. The biggest role plumbing plays in the games is usually mentioning that Mario is a plumber and Mario using Warp Pipes to his advantage.
 Notable Plumbers