Warp Door

Super Mario World
Warp doors are used in Super Mario World, mostly in castles to transport him to a different room. The most Warp doors have appeared in Bowser's Castle.

Super Mario 64
In Super Mario 64, Warp Doors (or just doors) have appeared in Peach's Castle to transport Mario to a Painting that leads to a level.

New Super Mario Bros. series
Doors have appeared at the end of every Castle, or Tower level that leads to the Boss of that area. Doors also appear in Ghost Houses.

Super Mario Maker
In Super Mario Maker, Warp Doors can be used as course elements. They transport the player to a different area of the level. Up to 8 doors (4 per area) can be placed in the level. As of the 1.20 update (November 2015), players can knock multiple times the door at the Course Maker to reveal Weird Mario. The 1.30 update introduces a variation: The P Warp Door that cannot be activated until pressing a P Switch. Another variation introduced on the 1.40 update (March 2016) is the Key Door; they can only be opened with a Key, another feature introduced in this update. If 2 to 8 Key Doors are present, the player must find 2, 3, 4, 5, 6, 7 or 8 Keys to open the respective doors.

Wario: Master of Disguise
Warp Doors have appeared in Wario: Master of Disguise. When Wario transforms into Arty Wario, he can draw a Warp Door. In order for it to appear, Wario must draw a large square with a line going through it, making the door appear. On top of the Warp Door is a pumpkin-like statue that is shown to be alive. The Warp Door takes Wario to the last save area he saved in.