World 5-4 (New Super Mario Bros. Wii)
From the Super Mario Wiki
The level starts in a area with Goombas falling from above, and four Hidden Blocks, one containing a Super Mushroom. The player must enter a Warp Pipe, which leads to a wooden plank that Mario must use to avoid the poison and reach the flagpole. A ? Block containing an Ice Flower is to the left of the exit Pipe. Enemies including Piranha Plants, Goombas, Koopa Troopas, Bob-ombs and even coins land on the plank, causing the numbers on the plank to increase from 0 up to 5, which causes it to turn red and stop moving. To make the plank start moving again, the player has to defeat enemies so that there are less than five. Later, a POW Block can be found and used to defeat the enemies on the plank.