There's a whistle in World 1 and a whistle in World 2. When you use one whistle, it takes you to that little warp island with three connected sections of pipes that warp you to different worlds. The top row has worlds 2-4; the middle row has worlds 5-7; the bottom row has world 8 – the last world.
Like I said before, when you use one whistle it takes you to the top row. Then if you use a second whistle while you're still on the warp island, it sometimes takes you to the middle row and sometimes takes you to the bottom row. This has always frustrated me like crazy!!
Is there a way to always guarantee you'll make it to the bottom row (with the warp to the last level) by only using two whistles?
Best Answer
I think you are mistaken -- using a warp whistle while in the warp island should always take you to World 8. The Super Mario Wiki confirms this:
There are also two warp whistles in World 1, as well as the third one in World 2. One is obtained in stage 1-3 by holding down on the D-Pad while standing on a white platform near the end of the stage. Another is obtained by using Raccoon Mario to float on over the top of the end of the Fortress stage in World 1. And the last is obtained by using the hammer item to break a rock in the top-right of the map of World 2. A video showing their locations is here: Super Mario Bros. 3 Warp Whistles