we got this one from a friend of ours:
bush opened the letter and it contained a single line of coded message:
no one could solve it at the fbi so it went to the cia, then to the nsa.
with no clue as to its meaning they eventually asked britain’s mi-6 for help. within a minute mi-6 cabled the white house with this reply:
“tell the president he’s holding the message upside-down.”
[ed. note: yes, we know there are capital letters in the joke. but our style sheet rule of “no caps” would ruin the punchline. sometimes you have to give up style for a laugh!]