P Warp Door

P Warp Doors are Warp Doors that can only be entered when a P Switch is active. These Warp Doors made their first appearance in Super Mario Bros. 3, but with a different appearance from its current one.

Super Mario Bros. 3 / Super Mario Advance 4: Super Mario Bros. 3
A P Warp Door first appears in Super Mario Bros. 3 (and reappears in its remakes) in the second fortress of Giant Land. This P Warp Door is invisible, and an outline of Blue Coins will show where to enter when the P Switch is pressed. P Warp Doors also appear in later fortresses including and, this time in visible form, represented as a white rectangular doorway.

Super Mario World / Super Mario World: Super Mario Advance 2
In Super Mario World and its remake, P Warp Doors, named Blue Doors, appear in the levels Donut Secret House, Vanilla Ghost House and Forest Ghost House. They have the same sprite as a Warp Door, but with a light blue palette.

Super Mario Maker series
In Super Mario Maker, P Warp Doors were introduced in the version 1.30 update, and available at the start in Super Mario Maker for Nintendo 3DS. They have new sprites for all styles, in the same blue as the P Switches with a white or blue "P". Unlike in Super Mario World, they are visible as outlines when not active.

P Warp Doors also return in Super Mario Maker 2, behaving exactly the same as in the predecessor.

Super Mario Maker

 * Play Nintendo: "Unlike regular Warp Doors, these are only visible while a P Switch is active – perfect for creating truly devious Ghost House courses."

Trivia

 * In the Ghost House of World 3 in New Super Mario Bros., there are doors that only appear during the effect of a pressed ? Switch, thus functioning in a similar way to P Warp Doors.