To hollow out a tall, skinny squash, scoop out the insides from the top and the bottom: Cut off the bottom with a keyhole saw, and use a plaster scraper to scoop out the wide bottom section until walls are 1/2 to 3/4 inch thick.
Cut off the top with the keyhole saw, and use an apple corer to remove the insides at that end. Carve features; replace the top for display, if desired.
Legend has it that the luckless souls who hear the Three Squashes' song of woe shall vanish into the nearest vegetable patch, never to be seen or heard from again. Since narrow squashes are easier to hollow out if you work from both ends, these guys had the tops of their heads cut off.