Can I post a personal one? My teammates thought it was hysterical! My workplace is pretty casual in dress - we mostly wear jeans and t-shirts, but are expected to move up to business casual if we have clients in the office. Usually an email is sent out a few days before to announce a visitor, but on occasion emails have gone out last minute. A friend of mine from a previous team I worked on texted me really early on Monday to tell me that an email had gone out to everyone the previous Friday saying it was business casual for Monday. He made it sound really good - just wanted to let me know, knows I work on a more high profile floor, etc. I freak out, pull out some of my nice clothes, hurriedly change - I show up in business casual Monday morning...and it was all a fake!
I was dressed really nicely too, so I totally stuck out for the entire day. Like I said, my whole team thought it was a fantastic joke.