For more than 30 years, Jocko Marcellino and Screamin' Scott Simon have made a living acting like their idols: doo-wop singers from the 1950s . They are the founders of Sha Na Na, the musical group with the grease and the goofy hit television show in the '70s. "They're not the latest hits, but they're the greatest hits," Simon says of the songs the group popularizes. "We're not stars. We didn't write the songs; we didn't sing the original hits." Nevertheless, the group built itself up into headliners, the most memorable of which was probably John "Bowzer" Bauman. Famous for a pose in which he simultaneously flexes a muscle and opens his mouth, Bowzer was that kind of greasy but intensely vulnerable character that really did exist in the '60s and in the '50s. Bowzer and the others are in their 50s now, and their music lives on. Sha Na Na sold millions of records, but they never had a hit of their own. They would interpret the hits of others; in a sense, they were the great pretenders. But it was all in fun, at least until one day, when a greaser with a great voice showed up in Florida fooled a lot of people. Danny C. was not just a great pretender; he was a great imposter, reports Correspondent Bill Lagattuta for 48 Hours.. Nothing seemed to stop Gerald Barnes, not even three more arrests and convictions for medical fraud. He didn't just lie to patients and doctors. He lied to his five wives. His last marriage in 1994 was to Lisa Roberts; he told her he was a doctor. "He was very charming," says Roberts. She never doubted that he was a doctor. Gerald Barnes:What drove this personable, smart man to deceive so many people? One psychiatrist who examined him called him "immature, extremely insecure... and depressed." But Barnes claims he was only interested in helping others.