"Cheesy Poofs" is indeed a fictional product but is believed to be a parody of the real product, Cheetos, produced by Frito-Lay. More information is available by clicking on the following link, http://www.fritolay.com/snacks/product-page/cheetos
When the show first came on in 1997, actual edible Cheesy Poofs (in the same box as the show) were released for a limited time.