Mario had many jobs:
Mario didn't start out as a plumber, but as a carpenter. For his first appearance in Donkey Kong it was decided that a manual labour job would make him a more appealing character in that game.
It wasn't until 1983's Mario Bros. that Mario would be depicted as a plumber, given the game's underground location.
In his 30 years of gaming Mario has also been depicted as a bottler (Mario Bros Game & Watch), a loader (Mario's Cement Factory), a soldier (Mario's Bombs Away), a wrecker (Wrecking Crew), a referee (Mike Tyson's Punch-Out) and a doctor (Doctor Mario