The initial script described the dog as a chihuahua (the title then was in fact "The Chihuahua").
When Chico returns the framed picture frame with the stamp, his doing so was achieved economically (from the perspective of getting the shot on film) by simply reversing the original shot of Chico picking up the picture frame.
Percy Rodrigues guest starred on Star Trek in the episode "Court Martial." Star Trek, of course, starred Leonard Nimoy as Spock.
In another drug reference, that may or may not have been intentional at the time of production, the character surname "Snow" is also slang for "Snow blow", a type of drug called a cathinone. It is similar to cocaine in that it is a short-acting stimulant drug. A number of different cathinones have been sold internationally as snow blow/snow/blow. In powder form, cathinones are generally a fine white, off white, yellowish or brown powder.
This episode aired on guest star Gregory Sierra's 33rd birthday (born January 25, 1937).