World 6-1
Head right past the first ledge and wall-jump up to the first Star Coin. Next, head right, wall-jump up, and go left to grab the second Star Coin. Go back to the right and continue. When you are above the third Star Coin, press 
to hang down and grab it, then press 
to continue, and hit the flagpole to finish the level.
World 6-A
Jump into the tornado to fly up. Follow the trail of coins to grab the first Star Coin. Come back down and let yourself sink to the bottom of the sand waterfall (it is higher than the surrounding area). You will enter an underground section. Wall-jump to reach the second Star Coin, let yourself fall down, and climb up on the right. Go through the yellow warp pipe at the end to exit this section. When you see a number of pipes close together, go down the yellow warp pipe near the middle. Jump over the Giant Piranha Plant to grab the third Star Coin. Exit through the red warp pipe on the left and go down the green pipe immediately next to you to be shot over the pipes. Continue to the right, go through the green warp pipe at the end, and hit the flagpole.
World 6-2
Go right and through the warp pipe at the end. At the first ?-block, swim up beneath the area between the two coins to reveal secret blocks and a vine. Climb the vine, go right, and hit the block from underneath. Hit the switch and quickly head right to grab the first Star Coin before time runs out. Continue to the right and enter the second green warp pipe to be shot forward. Go right some more and jump when the water is high to reach the second Star Coin. Head down the next green pipe to be shot forward again. Head right and come back to the left underneath to grab the third Star Coin. Go through the yellow warp pipe at the end and hit the flagpole.
World 6-Tower 1
Go up, taking care to avoid the moving spiky bars. When you see the first Star Coin at the fourth spiky bar, grab it and duck quickly to avoid being hit. When it leaves, continue up. When you reach the trampoline, duck to avoid the spiky bars. When they leave, jump on it to reach the next ledge. Continue up and go through the door. Head all the way up to the door. Wait for the spiky bars to leave and grab the second Star Coin. Then go through the door. To grab the third Star Coin, you must be Mini Mario or Luigi. If you have a Mini Mushroom, use it. Wall-jump and go through the green warp pipe. If you are Luigi, it needs precise timing. Jump off the Dry Bones when it is about to turn around. Start wall-kicking until you reach the platform. Wait for the spiky bars to leave and jump to the middle ledge. Wait until they leave again, grab the third Star Coin, and go back to the middle ledge. Exit through the green warp pipe when the spiky bars leave again. Go down and through the double doors. If you are Mini Mario, ground pound Bowser Jr. three times. Otherwise, jumping on him three times is enough. (Ground pound it once (two jumps), then you can just jump on it once.)
World 6-3
Jump from the jumping ?-block to grab the first Star Coin. If you can't jump on it, hit it from underneath to calm it. Head down red warp pipe and run to the right. Don't stay on the logs too long, as you will fall into the poisonous water. Exit through the pipe on the right. Go down the second pipe on the right to grab the second Star Coin. Go back out and go down the last pipe. Run right and exit through the pipe on the right. Hit the red block to stop its turning. Do a running jump from it to the left over the green pipe. Wall-jump to reach the third Star Coin and then exit above the green pipe. Run left and jump over the pillars. Hit the flagpole to finish the level.
World 6-4
Head right and up above the rotating fireball arms to reach the first Star Coin. Grab it and head right. All the way on the right, hit the red switch and go back to the new red blocks. Climb up and go left above the rotating fireball arms to grab the second Star Coin. Go back to the right and go through the red warp pipe. Head right over the thin ledges and moving platforms. When you reach the numerous small ledges, climb up and head right. Go through the green warp pipe, run all the way to the end, grab the third Star Coin, go back to the left underneath, and leave through the yellow warp pipe. Head up the green warp pipe near it and hit the flagpole.
World 6-Tower 2
Head up until you see the spikes pointing up. Climb next to them and go right to grab the first Star Coin. Continue up and go down the green pipe on the right to be shot up. Press 
to land upon the conveyor. Duck and let it bring you beneath the second Star Coin. Release and grab it. Jump up and continue up. Grab the horizontal rope and move forward to grab the third Star Coin. Go back to the left and down the green pipe to be shot up. Press 
to land on firm ground. Go through the doubble doors to battle Bowser Jr. once again. To defeat him, hit him with his shells three times. Once he has been hit two times, his shells will be faster. Fire Mario can also defeat Bowser Jr.
World 6-5
Head down the green pipe to start this underwater level. In this level, watch out for green fish who will swim towards you. Swim right and go up to the first Star Coin. Continue to the right. Go up the yellow warp pipe, grab the second Star Coin, and exit through the same pipe. Go right and down the whirlpool with blocks at its base. Grab the third Star Coin and exit through the red warp pipe. Go up the green warp pipe to the right and hit the flagpole.
World 6-B
Go down the green pipe on the right to be shot up. Press while in the air to land on the ice. Go right, jump on the swinging pole and release so as to land on the next block of ice. Once again, jump on the swinging pole, but wait for it to be completely at the right end of its path ro release and land. Jump on the next pole and repeat the last step. Grab the shell of the Red Koopa and throw it to the right to grab the first Star Coin. Jump on the next pole and release at the right-most point to land. Continue over the purple and orange mushrooms (be careful, they bend). Go down the pipe to be shot up and press while in the air to land on the green Paratroopa and bounce to the second Star Coin. Go down the pipe again and press while in the air to land on the ice. Avoid the Piranha Plants and continue right and down. Be careful on the purple and orange mushrooms. Go down any of the three vertical green pipes to be shot forward. Jump on the pole again, but this time, time yourself so as to grab onto the next pole. Release that pole at its far right to land at the top, duck, and grab the third Star Coin. Continue right and hit the flagpole to finish this alternate level.
World 6-6
Head right, jump on the spinner, fly right, and jump on the next spinner. Fly up and get on the next spinner above you. Fly slightly to the right to land. Jump up and get on the next spinner. Fly up and left. Go above the Chain Chomp and grab the second Star Coin. Go down on the left. Launch from the spinner and destroy the column of blocks. Hit the switch and grab the first Star Coin. Launch yourself again and fly right. Launch from the next spinner and fly right again. Head right and down. If you land, head to the bottom and launch yourself from the spinner. Land and run to the column of blocks to the right. Destroy it to unblock another spinner. Launch yourself from it, fall onto a red Paratroopa to go back up and hit the switch, hit the other red Paratroopa, and go in the green warp pipe at the top. Launch yourself up from the spinner and fly left. Jump to the right over the green pipe. When you reach the third Star Coin, wall-jump between the pipes to grab it (just follow the coins). Go down the yellow warp pipe and then go right. Go down several green pipes to be launched up. When you reach the top, you will be launched to the right. Go down the third green pipe you see there to hit the flagpole, finish the level, and gain a life.
World 6-Castle
When the sliding platform comes out, head right. Grab a Red Koopa shell and throw it towards the first Star Coin to grab it. When you reach the second Star Coin, let yourself fall onto the bottom platform. Grab it and then jump back up when the platform comes out again. Continue to the right. After the checkpoint, head up and right. Do a running jump to reach over the vertically-moving blocks. Head right and grab the third Star Coin. Go back to the left, and now go between the blocks. Head right and through the door. Go up on the platforms and then through the double doors. To defeat this boss, jump on him three times. It sounds simple, but after every hit, he goes up one level. To reach his top level, you must jump onto a Bullet Bill and then on top of him. He will also throw Bob-ombs, so be careful. You can also jump on the bob-ombs and then pick them up and throw them at him. Grab the shining key to finish this level and advance to World 8