World Flower-6: Shiftier Boo Mansion

Right at the start, a Big Boo will pop up behind you. It's guarding the first Green Star #1. You'll need to lure it away so you can sneak past and grab the star. Just ahead, you'll see a moving ?-Block. Jump on that to reach a higher one that's got a power-up, likely a Fire Flower. Ignore the lower path to the right – that Warp Box is a fake!

Head upstairs and hop onto the couch. Ride it all the way to the top. Look for some invisible cloud platforms up there. Jump onto them and head to the right to find Green Star #2.

Keep going through the door at the end of the area. You'll see a Goal Pole, but it's fake, so ignore it. Go through the door on the other side and head left down a long hallway. You'll see a bunch of fake 1-Up Mushrooms, but one is real! Watch out for Big Boos too. Right before you reach a pit at the very end, you'll find Green Star #3. Be careful, though, because the floor will start moving as you try to grab it.

Enter the nearby door and run to the right, jumping over the line of Peepas. You'll run into another fake Goal Pole. If you go to the very end of this section, you'll find a Warp Box. This one actually takes you back to the beginning of the outside area.

So, to find the real exit, when you reach that fake Goal Pole, you need to run to the bottom left corner. Underneath the bridge, you'll find a hidden Warp Box, along with some invisible cloud platforms. Take this Warp Box, and it'll lead you to the real Goal Pole to finish the level!