I best remember his performance as Jack, the refrigerator repairman's assistant, in an episode of All in the Family. As a pre-teen white kid growing up in the Rockies I saw the character not merely as comic, but rather as unbelievably cool. (Something I eventually grew out of, unlike most of the 2008-2012 U.S. electorate.)
"Barney Miller", where Glass played a detective who was an aspiring writer. "BOB: 'Blood on the Badge'" was his book. Always impeccably dressed and when he thinned out his wardrobe he ditched his uniforms to make room for his suits -- hilarious show. And he was in the short-lived SciFy series, "Firefly".