It might be possible to automatically hide messages in jokes. Researchers have figured out that certain kinds of jokes are good candidates for automated word substitution, rendering them a decent carrier for very short hidden messages.
The trick seems to be the advent of homophone/homograph/honomnym dictionaries, so that software can now write automated puns.
The method does fall down a bit when you think of it over a long message, many jokes, and Kerckhoff conditions (adversary assumes a message is there & knows all about the system except the keys used for encryption and hiding). Carrying a long list of jokes is a bit more conspicuous than a message in a movie… and in order to encode meaning besides “does this codeword exist in the text or not” you have conceal knowledge of which variation or word* is significant to the sender — which to my eye is harder than it seems at first.
* word in the case of several jokes, a subset of which contains the hidden message while the others are dummies
“…secreting a message within normal text usually disrupts the grammar and syntax or the spelling and so immediately looks suspicious. Now, an approach that is far less obvious and is tolerant of poor grammar has been developed by computer scientist Abdelrahman Desoky of the University of Maryland in Baltimore County, USA and is described in the latest issue of the International Journal of Security and Networks.
Desoky suggests that instead of using a humdrum text document and modifying it in a codified way to embed a secret message, correspondents could use a joke to hide their true meaning. As such, he has developed an Automatic Joke Generation Based Steganography Methodology (Jokestega) that takes advantage of recent software that can automatically write pun-type jokes using large dictionary databases. Among the automatic joke generators available are: The MIT Project, Chuck Norris Joke Generator, Jokes2000, The Joke Generator dot Com and the Online Joke Generator System (pickuplinegen).
A simple example might be to hide the code word “shaking” in the following auto-joke. The original question and answer joke is “Where do milk shakes come from?” and the correct answer would be “From nervous cows.” So far, so funny. But, the system can substitute the word “shaking” for “nervous” and still retain the humor so that the answer becomes “From shaking cows.” It loses some of its wit, but still makes sense and we are not all Bob Hopes, after all.”