M-x spook adds a line of randomly chosen keywords to an outgoing mail message. The keywords are chosen from a list of words that suggest you are discussing something subversive.
The idea behind this feature is the suspicion that the NSA1 and other intelligence agencies snoop on all electronic mail messages that contain keywords suggesting they might find them interesting. (The agencies say that they don't, but that's what they would say.) The idea is that if lots of people add suspicious words to their messages, the agencies will get so busy with spurious input that they will have to give up reading it all. Whether or not this is true, it at least amuses some people.
You can use the
fortune program to put a fortune cookie
message into outgoing mail. To do this, add
(add-hook 'mail-setup-hook 'fortune-to-signature)
You will probably need to set the variable
 The US National Security Agency.