This one happened impromptu. A group of us were novice UNIX hacks working
for our department of computer science, all on similar terminals. I had
written a small program that would transmit a single character at a time to
another terminal (No big deal, but no one else had tried it). One guy was
typing away, and I was making his cursor "wiggle" by pressing the forward
and reverse arrow keys. He exclaimed that something was wrong with his
cursor. Another guy picked up on this, and explained that the cursor beam
must be loose. He gave the right side of the first guy's (John's) terminal
a good hard whack, I transmitted a carriage return. John laughed, but
actually sat there typing in (some text), and whacking the side of the
terminal every time he needed a carriage return, FOR SEVERAL MINUTES.
Needless to say, we were hysterical.
        The second guy, (Tim), said "John, watch this!" and put his hand
under John's desk and gave the underside of the desk another whack: I
transmitted a "HOME" character, moving the cursor to the top of the screen,
again as if the whack had moved the cursor. John continues typing, whacking
the bottom and side of the terminal whenever he needs cursor motion. Tim
smacks the top of the terminal and I transmit a CLEAR key: it looked as if
the characters have been "knocked" off the screen. John is just about the
get the lab manager when we clue him in.