TV
I've seen Westerns, I know how to speak cowboy. (to bartender) Dry white wine and Perrier please. And what about you two chaps?
— Rimmer · Red Dwarf

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker boasts that watching Westerns has taught him cowboy language, then immediately undercuts himself with a refined drink order and the word 'chaps'. The joke rests on the gap between his confident claim and the very different manner his own words reveal.
Context reviewed