Ok I give up I don’t have any material and don’t feel like preparing any because the influx of IMO problems, including the shortlist, is too fascinating. Instead, here is a joke quoted verbatim from TVTropes (CC-NC-SA).
An American anthropologist has been studying a tribe in Africa by living with them for a year. One day, the chief called him into the chief’s hut. The chief sighed. “Well, my friend, it seems that we must ask you to leave.