The Wrecking Crew universe (レッキングクルー, Wrecking Crew) refers to the Smash Bros. series' collection of stages and properties that hail from the NES title, Wrecking Crew. It is a sub-universe of the Mario series, and has no characters that hail from it.
Before Mario had cemented his occupation or abilities, Mario and Luigi would have numerous jobs from game to game. In the Wrecking Crew sub-series, their role is that of demolition workers. Wrecking Crew was released in 1985 for the Famicom and NES. In this game Mario could not jump, so he had to approach levels methodically, demolishing them in the right order all while avoiding enemies. It is notable for being one of the first games with a custom level editor.