A White Mushroom House appears after you meet a specific course’s coin target and finish that course. The seven challenges belong to Worlds 1–7; Dark Land has no corresponding house. Odd-numbered worlds give P-Wings and even-numbered worlds give Anchors. The houses look blue in some remakes.
The coin target concerns coins collected during that run, not simply the number already shown on the counter when entering. Plan the attempt before clearing the stage, because a completed course cannot normally be selected again in the original NES game.
World 1-4 — 44 coins, P-Wing
Use both multi-coin blocks as well as the airborne trail while keeping pace with the scroll. Open World 1-4 route.
World 2-2 — 30 coins, Anchor
Take the oasis coins, activate the hidden P-Switch and collect the converted bricks. Open World 2-2 route.
World 3-8 — 44 coins, P-Wing
Use the vines to stay above Boss Bass and combine normal coins, the multi-coin block and P-Switch route. Open World 3-8 route.
World 4-2 — 24 coins, Anchor
Aim for all twenty-four coins. Collect the ordinary coins ahead, return to the switch and time its use with the rising terrain. Open World 4-2 route.
World 5-5 — 28 coins, P-Wing
Collect the coin groups around the Donut Lifts, including the lower coins, without losing the scrolling route. Open World 5-5 route.
World 6-7 — 78 coins, Anchor
Collect the full scrolling route and use Fire Mario to thaw the final frozen coins beyond the pipe. Open World 6-7 route.
World 7-2 — 46 coins, P-Wing
Wear a Frog Suit and collect the complete underwater P-Switch route before finishing the level. Open World 7-2 route.
Use the reward
A P-Wing provides sustained flight for the next stage while its effect remains intact. Keep away from enemies and hazards; it does not protect against lava, crushing or a fall below the level. An Anchor keeps an airship from changing position after an unsuccessful attempt. Use either from the world-map inventory before entering the intended stage.