The Cress Covered Keyboard Prank. Crazy Swedes with too much time on their hands.
After that it was time to pour the cress seeds into the gaps between the keys. The seeds required some blunt persuasion to take their places. An old creditcard came in handy. This took far longer than I had expected. The reason I did not place the seeds directly on the cotton before replacing the keys was that I wanted the cress to come up between the keys.