This level will introduce (and be the only level with them) the Grumblumps, large blocks that act like obstacles and aren’t really enemies. They will simply rotate and you will need to stay on top of them as they do, since the Grumblumps will be over lava and that spells instant death if you touch it. It’s generally a bad idea to jump while on the Grumblump, so you should only do that when it’s necessary or as a last-ditch effort. The first Grumblump will have Skipsqueaks on it, so follow their example in moving from one side to the other, as the block moves.
Cross the first Grumblump and as you’re riding the second one, it will pass by some pillars that have Fire Piranha Plants on them. Their fireballs shouldn’t really hit you, but you will need to jump off the Grumblump to grab Green Star #1. Also, whenever the Grumblump falls to a lower area, don’t worry and keep calm. Once you reach the end of the second Grumblump’s journey, you can find a block with a power-up in it (Super Leaf). Cross the bridge and feel free to ignore the Hammer Bros, using the Jump Panels to reach the Checkpoint Flag. Note that if you die from now on, you can backtrack to the ?-Block and grab a power-up.
The next bit can be challenging, as the collectible you are trying to grab is above an enemy, that’s on a small pillar. As you ride the next Grumblump, it will slide down a hill and you will see a Hammer Bro on a pillar right in front of you. You will find the Stamp is above that Hammer Bro, so you need to jump on top of him to get the Stamp and try to land on the pillar. Get back on the Grumblump, riding it to the end. The next section has you dodging Splorches, with there being a Green Star Ring here. Collect all of the coins to get Green Star #2, then continue to grab a power-up from the ?-Block.
The following Grumblump will be the final one, with some Skipsqueaks falling on it during its journey. You can ignore these completely, as they won’t get in the way and will fall off on their own. Not long after the first set of Skipsqueaks fall, the Grumblump will stand tall and you will need to jump up to grab Green Star #3. When you reach the hill, that will be the final bit, with the Goal Pole right below you. As the Grumblump stands tall and starts falling down, you’ll need to perform a long jump to the pole. If you have a Cat Suit, then this isn’t necessary, of course.