Dreamer.
Hey, you weren't complaining on that flight last week when the flight attendent said "make sure everything is in its upright position"
Practical Joke -- Real World ZOT!
Electroplate a troublesome user's keyboard with silver (conductive) paint. (Use the supplied silkscreen to match the original appearance.)
Connect the entire assemblage to the 120VAC outlet.
The moment said user touches a key with both hands, break out the marshmallows.
(Yes, I've had some rough days to have thought of this...)