IOWA CITY, IA—Shawn Sullivan, 22, was stunned to learn Monday that his father is familiar with the Johnny Cash song "I Walk The Line." "Where the hell did Dad learn that?" asked Sullivan, whose father recognized the song playing over speakers while dining out with the family. "That's, like, something me and my friends listen to." Sullivan conjectured that, while borrowing his father's car recently, he must have inadvertently left the radio tuned to KRUI 89.7, the local college radio station.