oh man! there use to be back in the win2K days, but they cut it out a loooong time ago!
I use to sit in the school library and send messages to less than tech savvy kids with things like:
"Your computer is about to explode in 5"
"4"
"3"
"2"
"1"
and watch them jump up lol
Or messages like "Man, you've got some ugly hair today" and watch them look arround the room all self conscious.
... perhaps I was a messed up kid... but those were good times