Several years ago, back when the internet was still in its earliest stages, our office had e-mail that extended just within the office itself. The office was pretty small, maybe 40-50 people. Also, our computer "network" extended just within the walls of the office--only good for sharing files within that physical location.
I had a higher "security" rating on that primitive network, so on March 31, after hours, I created an e-mail account with a name similar to the boss's ("Richard K----" instead of "Rick K----"). I wrote an e-mail imitating his rather pompous writing style in spelling out new standards for the office, things like:
-- Sign out sheets for paper clips
-- Don't use the office copier for less than 10 copies--if you have fewer, wait for someone else and "copy-pool"
-- Print queues for the computer printers now operate in alphabetical instead of chronological order
-- All client meetings must be conducted in navy blue suits. All personnel should bring in a navy blue suit to leave in their office to change into for "emergency meetings"
And so on. The e-mail was read on April 1, of course.
Quite a few people actually believed it until the more rational members of the office reminded them to look at the date of the e-mail.