World 9-8 (New Super Mario Bros. Wii)
From the Super Mario Wiki
World 9-8 is the eighth and last level of World 9 in New Super Mario Bros. Wii. It is unlocked by collecting every Star Coin in World 8. Like all levels in World 9, there is no midway point. The most prominent features of the stage are the bouncing clouds and the King Bills, which only appear in this stage.
The last stage of the game is a sky level reminiscent of Coin Heaven. In it, the "floor" is made of several Bouncy Clouds that let Mario jump every time he falls on them. A little ahead, two ? Blocks are found, one of which contains a Propeller Mushroom. A little more forward, the first Star Coin is found surrounded by Fuzzies and after this part, a Roulette Block is found surrounded by five Fuzzies, one being big. Below them, a ? Block from the right contains a Mini Mushroom that can help the player to access high places. After that, the second Star Coin is found alongside several Fuzzies.
Forward, King Bills begin to break down walls so Mario can continue his progress. The level forewarns the player of the King Bills with large Bullet Bill-shaped coin formations. The third Star Coin is found stuck between walls that a King Bill destroys. Arriving at the end of stage, a last King Bill appears near the flagpole, where it can be destroyed if the player jumps on the flagpole before being hit by it. A P Switch found in a nearby Brick Block indicates this last King Bill with a Blue Coin arrangement instead. This course has the background from World 7.