World 9 is a bonus world in New Super Mario Bros. Wii that is unlocked by beating the game. It is a world that is the shape of a star. It is rainbow colored and is named Rainbow Path. Unlike other world levels, to play the first level, you must find all Star Coins in World 1. The number of the level in World 9 tells you, you must go to the world with that same number. If you wanted to unlock World 9-2 you will have to find all Star Coins in World 2. Some enemies only appear in this world such as King Bills. Most levels are mix-ups of two worlds. This level in the picture is mixed with World 5 and World 3.
World 9-1Although this stage is unlocked for World 1, the layout is similar to World 7-1. There are lots or spinning, rectangular platforms around the level. Also appearing is a big L-shaped platform that is also spinning. Like all World 9 levels, there is no Midway Point, making it difficult to traverse the level. Koopa Paratroopas are the main enemies in this level.
World 9-2This stage takes place on a beach setting. The player must get to the goal while avoiding a Porcu-Puffer and many Koopa Troopas. In this level there are lots of spots where players can fall. A Cheep-Chomp makes an appearance here.
World 9-3This course has the background of World 6. It features Missile Bills and Missile Banzai Bills. POW Blocks cannot defeat these enemies. The floor resembles that of World 7-2.
World 9-4World 9-4 has a desert landscape, which has many Warp Pipes and auto-scrolls. Most of the enemies in this level are Venus Fire Traps and Bob-ombs. The level's main Power-Up is an Ice Flower, which is required to get a Star Coin.
World 9-5A snow level, where the player must get to the top of the icy mountain, while avoiding Cooligans, Fuzzies, and Mega Fuzzies. The first Star Coin is just outside a Warp Pipe that spawns Cooligans, and can be easily obtained by sliding with the Penguin Suit. The second one is near another Warp Pipe, and can be obtained with a Wall-Jump, though sliding is still recommended. The last one is tricky, as the player must freeze a Fuzzy to use the Fuzzy's ice block as a platform to reach the Star Coin.
World 9-6A lava level, where platforms emerge and descend into the lava. The only enemies in the entire level are Fire Chomps, which can make the level a bit more difficult.
World 9-7Although this is the penultimate (next to the last) stage, it is very difficult. The level takes place in a snowy forest, with floors made of ice blocks and Warp Pipes. Venus Fire Traps, Piranha Plants, and Fire Bros. appear in this level, using their fiery attacks to burn open chestnut shells that reveal Goombas, and melting away the landscape. This makes it difficult to traverse the level. Munchers also appear in this level. The first Star Coin is found near the beginning, between some Venus Fire Trap Warp Pipes. The second one requires the use of Fire Mario or Venus Fire Traps to melt the ice blocks covering the Star Coin. The last one can be obtained by letting the Fire Bro. use their own fireballs to melt the ice, and Wall-Jumping or using Propeller Mario.
World 9-8The last level in the game is a sky level. In it, the "floor" is made of several clouds that let Mario jump every time he falls on them. A little ahead, two Question Blocks are found, and one of them contains a Propeller Mushroom, which can improve a player's chance of surviving greatly. A little more forward, the first Star Coin is found surrounded by Fuzzies and after this part a Random Item Block is found surrounded by Fuzzies, one being a Mega Fuzzy. Below them a Question 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 Fuzzies. Forward, King Bills begin to break walls so Mario can continue his progress. The third Star Coin, is found between walls that a King Bill will destroy. Arriving at the end of the level, a last King Bill will appear near the Flagpole, where it can be destroyed if the player jumps on the Flagpole before being hit by it. This level has the background of World 7-6.