Why do our brains go crazy for the melted cheese on a Philly cheesesteak or the crispy fried goodness of scrapple? (And what is scrapple anyway?) This week on The Sporkful we feast on some classic Philadelphia fare, then bring samples to a scientist at the Monell Center to find out what makes greasy treats so irresistible. If science were always this delicious, Dan would have a Nobel Prize by now.