Hideo Kojima once intended for the disk one of his games came on to release the smell of blood to complement the gameplay.
According to his Twitter (translated by Andriasang), Kojima's idea for the PC88 version of Snatcher was to coat the floppy disk in a special paint that would melt when it got hot and "release the smell of the crime scene".
The melting paint would also reveal text written on the disk, which might be used to solve an in-game puzzle.
The idea was, not unsurprisingly, shouted down and scrapped, but Kojima did of course go on to make players think outside his games in later years.
In the original Metal Gear Solid on PlayStation it was famously only possible to defeat Psycho Mantis by physically plugging your pad into the second controller slot. Otherwise Mantis just dodged everything you did.
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