"Estar de 'Rodríguez'" (loosely "stay as a 'Rodríguez') is a well-known idiom in Spain, meaning a husband who stays behind at home to keep working during summertime while his wife and children go on a vacation. Several sources point to this movie, which happens to have that very plot and a title character called Rodríguez, as the origin of the idiom, but the fact that the book "Panorama español contemporáneo", published one year earlier (1964), already includes the phrase used with its full meaning and without any cinematic connection, shows that it is actually the other way around: the movie's concept and title just come from the already existing idiom. The actual origin is most likely that "Rodríguez" is kind of a stereotypical office worker's last name in Spain, and since at least in that era the most common thing for bosses was to call their male employees by their last name (without the "Mr."), to "stay as a 'Rodríguez'" would be to stay where one would not be called by his first name as a spouse would, but by his last name, that is, at one's workplace.