To warp from World 5 to World 8, enter the World 5 Ghost House and get a Mushroom from the blocks. Then, go upstairs untill you reach an area with three brick blocks on the left side of the screen. Stand on top of them and jump to reveal three invisible blocks. Next, wall jump on the left side to get on top of them. Stand on the middle raised block and duck, then jump to reveal a block with a vine in it. Climb up the vine and a Boxing Ghost will appear. Jump off the vine to avoid taking damage from it. Kill it and climb back up, and enter the door. Kill the two Walking Pumpkins and stand in the middle. The platform will wobble and as long as you stay in the center you should be fine. When it reaches the top, exit and jump on the flag pole. A path will open to the Warp Cannon on the World Map. Enter and use the Cannon to warp to World 8.