I was gathering a few logs to see what they do, and I shaked all of them. After a while, I heard a wee voice call out to me, asking me to liberate them. So I split the log, and a mischievous leprechaun (or something similar) appeared and proceeded to drop every item in my inventory (not in the backpack,) to the ground.
I don't know if there are other kinds of leprechauns that you can 'get', but take care not to be near any other objects when splitting these logs, or you won't be able to pick up your stuff!