The Helmet is a key item that appears in Super Paper Mario.
Once the heroes tried to get into Outer Space, they couldn't breathe forcing Tippi to bring them back to Flipside. Merlon said he had a Helmet to use but gave it to a young boy as the Goldfish Bowl. Mario, Princess Peach, and Bowser managed to find Pook who was using the Helmet as a bowl for his pet fish Captain Gills. Pook was more than happy to give up his bowl as Captain Gills has gotten too big for it and asks them to let Captain Gills go in the water in the basement. After they have done so, the heroes can then use the Helmet to access Outer Space.