Plumber

From the Super Mario Wiki

“The plumber is mightier than the sword.”
—Old Mushroom Kingdom saying, Super Mario RPG: Legend of the Seven Stars Nintendo Player's Guide

Salvador Drainado, the greatest plumber of all.

A Plumber is an occupation that exists on both the Real World and Mushroom World. In the real world, their job is mainly to unclog toilets, however they do fix pipes occasionally. However, on Mushroom World, a plumber's job seems to be more to clean and maintain various sewers and fix Warp Pipes than toilets. While it is not required, a plumber who hopes to receive an award, such as the Golden Plumber's Helper has a better chance if they enter the Plumber Academy first. There is even a Grand Order of Plumbers. In The Super Mario Bros. Super Show! and The Adventures of Super Mario Bros. 3, several plumbers appear, such as Mario, Luigi, Mighty Plumber, Marco Polo's Plumbers and Salvador Drainado.

The first plumbers who appeared in the Mario series were Mario and Luigi in the game Mario Bros. Here, the Mario Bros. cleaned the sewers of the foul monsters that infested them.

Statues of Marco Polo's Plumbers, two great plumbers.

Plumbers have done great deeds. For starters, Mario and Luigi have saved Princess Peach, the Mushroom Kingdom, several other kingdoms, and even the whole Mushroom World numerous times. Marco Polo's Plumbers introduced plumbing to Venice from China and made it the city it is today.

While Mario's profession isn't often a heavy focus of the games, it did get passing mention in Paper Mario, as 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 fact, it is mentioned quite often that Mario is a plumber, and he quite often uses pipes to his advantage. However, plumbing has also been somewhat shadowed out of the series-- In Paper Mario: The Thousand-Year Door, Mario gives his profession as "adventurer."

While the only time Mario and Luigi are seen plumbing in the games (save for Mario Bros.) is briefly during Mario & Luigi: Superstar Saga (where they get to fix the Beanbean Castle Piping System, which has plenty of leaks), in The Super Mario Bros. Super Show!, they own the Mario Brothers Plumbing business. The Super Mario Adventures comic seems to portray them as plumbers, as the comic begins with Mario and Luigi being called to Princess Peach's Castle in order to fix a sewage problem.

In Nintendo Comics System, Mario's hero, Dirk Drain-Head is presumably a plumber.