The Flintstones (1994)

Continuity mistake: When the unconscious Barney is lying on the cart with the children, he has his head on his arm and his other arm is lying along his side. When, a few seconds later, you see this shot from further away, the positions of his arms have changed.

Cliff Vandercave: I want you to fire Bernard Rubble.
Fred Flintstone: Done! Wait, fire Barney, why?
Cliff Vandercave: Well, he scored the lowest on the company aptitude test. He's an imbecile. The company can't afford to have dead weight like him on the payroll.
Fred Flintstone: But Mr. Vandercave, he's got a new kid, a mortgage, I'm his best friend, I can't.
Cliff Vandercave: Look, Fred, if you don't fire him, I will, and then I'll fire you.

Trivia: When Fred is about to be hanged by the furious crew, Barney arrives driving an ice cream van, the music of this car is the song of the Jetsons, another cartoon from the team Hanna & Barbera.

Question: On Fred's first day of his new promotion, he says "I'm only one man, Barney." To which Barney responds."Not from the back" and they both laugh. Could someone please explain this gag to me. I have tried for years to understand it, with no luck.

Gavin Jackson