Besides being Barney Fife in The Andy Griffith Show show for many years, Knotts also did a bunch of memorable comedy movies during the 1960's, too. Who could forget The Incredible Mr. Limpet, The Love God, and The Reluctant Astronaut? Younger people remember Knotts as the apartment manager in the later seasons of Three's Company, in many ways an underrated role.
He will be sorely missed. 