Frank Nelson
One of the nice things about the first two seasons are the appearances of Frank Nelson, the "wise guy" who appeared for many years with Jack Benny and on many "I Love Lucy" episodes. Could it have been his Jack Benny co-star Mel Blanc who talked him into appearing on "The Flintstones"?
In "The Hot Piano" he's the piano salesman. ("Fingers. Fingers. Fingers.")
But my favorite is "Wilma's Vanishing Money" (also one of the most clever episodes in general) which contains perhaps the ultimate Frank Nelson line:
Fred: Cut out the comedy. I want to be treated like a customer.
Clerk: All right, but you won't like it.
And later when Fred tries to return his bowling ball:
Clerk: What's wrong with the ball?
Fred: My fingers won't fit the holes.
Clerk: They might if you washed them.
A hilarious insult because it makes no sense.
Too bad he didn't appear at all after Season Two.
Mice work in mysterious ways.
No, dear. That's God.