One luminary at the 95th Alfalfa dinner on Saturday night was CBS News anchorwoman Katie Couric, who came dressed in a strapless, shimmering, copper-colored gown and was one of the last to leave the party. She was hotly pursued by several eligible Alfalfans at the Capital Hilton. Couric left by herself, but most curious of all is whom she arrived with — WJLA-TV Chief Executive Officer Fred Ryan.