Mr. Rockhead Sylvester Nate Oscar George Slate is Fred's boss at the Bedrock Quarrel and Gravel Company. He is voice by John Stephenson.
Mr. Slate was born in Granite Town and lived at 140 Boulder Avenue. Right next door at 142 Boulder Avenue lived his sister Flo Slate Rubble mother of Barney Rubble. See Season 3 Episode 2: Fred's New Boss
An ongoing gag with Mr. Slate is that they always add new names. It has changed from Sylvester to Nate, Oscar and even George.