I've had the rats in an old rotting crate twice - the first time it wiped out 6 settlers, including both my doctor and other healer - the second time I had better medical and only a couple of people got sick. I've also had a strange book that caused a islander to take off and never come back, helpful honeybees, and a good monkey who messed with the research table and made 9,000 tech points. Also my first child mauled by a monkey when I told her to chase it away, but she did survive. In another game I had the whale and was given the choice of helping to free it or slaughtering it for food, I think. I feared by helping my master farmer might get pulled out to see by it, after my bad luck with so many other things. Had a monkey who was caught stealing food and the villagers found a stash of bananas that increased my food points, and several storms that wiped out all the food. I haven't gambled on any vials or any more crates since they've all been rotten so far.