As an in-joke, many later computer programs (not only games but also applications) include a hidden xyzzy command the results of which range from the humorous to the straightforward.
Many cadet units have their own in-joke terms for an unfriendly force, normally stemming from some joke about a fellow cadet member who is of a foreign nationality.
Moreover, entering certain words or phrases would replace the entered phrase with another, usually either an in-joke, or continuation of the comment entered.
