Blond, balding and bearded goofy comic actor-writer Chris Elliott honed his craft throughout the 1980s under the sarcastic guidance of David Letterman, the beloved former "malcontent" of "Late Night". Son of the venerable humorist-performer Bob Elliott (one half of the celebrated whimsical duo Bob and Ray), the younger Elliott was an NBC tour guide in NYC when his future mentor arrived with his mother. The quick-witted youth amused Letterman by offering him a children's admission and impressed him with his lineage. A few years later, Elliott was working as a gofer for "Late Night" and