Grand Star #4: Sinking the Airships
The first airship has some Octoombas and a crystal with a few Star Bits in it. There is also a Coin Bulb on the ground. In order to go to the next airship, you must take the cannon, and then blast yourself to a pole with a Pull Star on top, so that you don't fly into outer space. It is highly recommended to pull yourself to the Pull Star, since it will be less risky than the pole. You also need to watch out for circling spiky meteors, because if you get hit, you will fall and die.
The second airship has laser-shooting enemies, and a Magikoopa, along with another cannon, which will lead to the third airship. Watch out for the Bullet Bills, because they can Home Attack on you. The third airship has 2 Wigglers that will give you some Star Bits. There is also a spinning thing that will give you Star Bits once you spin on top of it. There is also a Coin Bulb and a Hungry Luma that will give you a 1-UP Mushroom or a Life Mushroom for 30 Star Bits. Go to a bridge, while avoiding a Bugaboom enemy to go to the extra platform. Spin next to a switch to go forward. DO NOT JUMP BACK! If you do, you will fall off and lose a life.
While you are on the platform, cannonballs, a 1-UP mushroom, and some Star Bits will appear, along with spiders. Once you get to the last airship, take the Sling Star to go to the boss. Bowser Jr. (on another airship) will say, "You just don't give up! Fine, then. I guess I'll just whup you myself! You want this Grand Star so bad? You're gonna have to take it from me!", I order to defeat him, you have a grab a Koopa Shell from a defeated Koopa Troopa and shoot it to the airship to beat the level, and once you defeat him, he will fly away, before exploding, releasing a Grand Star for you to collect. The power of the Grand Star will unlock the Bedroom.