Sci-Fi is a fantastic vessel for satire and Hitchiker's Guide to the Galaxy is a strong example of this. One of the most comedic and poignant pieces of satire in the radio show and book is the criticism of the bureaucratic state. It starts with Arthur Dent's house as it's about to be knocked down to build a bypass. Arthur brings up that in order to see the plans he had to go to a cellar and this, to the planning office, is considered "on display." This is then echoed by the Volgons coming to destroy the Earth for the same reason, and when the people of earth scream and panic the Volgons have the same excuses as the demolition crew has for Arthur.
This is actually a fairly masterful transition because it shifts the listener's perspective from an accessible piece of satire, commenting on something that could feasibly happen, to a more fantastic world, where aliens are coming to blow up the earth. The theme of bureaucracy continues on, for example, the guide talks about how Volgons won't save their grandmother without orders signed in triplicate, ect. This is a comment on the red tape and inefficiency of bureaucracy wrapped up in the humorous scenario of an old lady being eaten by an alien monster.