I had a friend who was a C64 guru. He knew the exact sequence
of peeks and pokes that could cause damage to the peripherals,
and when a store pissed him off, he'd code it on their demo boxes.
They triggered a sequence once, after it flashed a warning on touch.
Since they were too stupid to realize turning it off would wipe
it clean, they had several boxes on for a huge amount of time,
yet were scared to touch them.