Most dangerous animals in Australia (pt. reasons for why you should come to Australia. Jks but seriously I live in Australia and the only things (on this list) I've actually seen here are red backs, wallabies, huntsmans and kangaroos
Planting a garden in a keyboard. Best office prank idea, especially if the co-worker goes on vacation for a week or so. I would use a keyboard that looks like theirs though. That way you don't get into trouble for destroying someone's property.