Start off by jumping into the clear pipe and blasting yourself over to the next platform. There will be an Ant Trooper here carrying a Super Bell, so grab it for the Cat Suit, as it will be needed. Continue along, ignoring the Ant Troopers coming out of the pipes, as they will keep spawning. The second set of ?-Blocks here will have another power-up (Super Bell), so collect it and keep going until you spot another clear pipe. Ignore the clear pipe, and climb up the wall to the left of it to reach an alcove with Green Star #1 inside. There will be some invisible blocks right underneath the opening, so you will have to approach it from the sides.
Now fire up, up, and away past the Fuzzies to reach the top of the mountain. Carefully make your way past the rotating platform and grab the Coin Box Hat on the thin ledge. Use the nearby clear pipe cannon to launch yourself onto a large open area. Run around the near side to spot a bunch of clock pickups, then touch the Checkpoint Flag. There is also a giant rabbit near where you landed, but it just yields a bunch of coins if you catch it. A little north of the large rabbit will be a ?-Block, which contains a power-up.
Continue north and you will spot four rabbits, but three of them will yield nothing. Go after the one that’s glowing green and catch it to get Green Star #2. As you march on northward, you will find some Ant Troopers marching from a pipe and into a hole. Clear out a couple of them, then drop into the hole to find a Big Ant Trooper that has the Stamp on its back. At the northern end, enter the clear pipe and navigate your way past the Fuzzies, exiting at the top. At the top, you’ll find a Green Star Ring that puts four Green Coins on each rotating platform. You have to contend with Ant Troopers to get Green Star #3, but it shouldn’t be too hard. The Goal Pole will be right past this.