One of the most prominent allusions in Fahrenheit 451 is present in the form of the Mechanical Hounds.
It's a fairly common literary device, especially in science fiction, to use machines and mechanization to represent oppression; consider a film like The Terminator. Considering their role in the society of Fahrenheit 451, it seems clear that the Hounds fall into this interpretation as well:
- The Mechanical Hounds are not only mechanical, but unnaturally so; their eight legs, needle-nose and compound eyes make them abominations, "hounds" in name only, since they only superficially resemble a dog. This could represent man's corrupted interpretation of nature, our "inability to play God", as demonstrated in stories like Frankenstein: the Mechanical Hounds are like Victor's Monster, built in the image of a good thing, but having turned out horribly wrong.
- The Hounds have also been perverted in terms of their purpose and their analogy to a real firehouse dog; whereas real dogs were meant to find trapped people by scent, the Hounds track people by scent and kill them, or otherwise impose a violent force of will. The Hounds represent a complete dystopian image, where the familiar has become its own ideological opposite.
- The Hounds are employed as tools of the Government; for example, when a Hound fails to catch Montag, the government selects a random victim to demonstrate that the Hound never fails, and the government always gets its way.
Thus, the Hounds are allusions to totalitarian control, "perverted" science and technology, and the corruption of society.
Other allusions might include the television, an allusion to the individual choosing ignorance, and the railroad tracks, an allusion to "old times" and "safe" technology.