I remember a discussion about whether there would be money in the "new order." One person argued that Adam and Eve didn't have money, while the other argued that there would have to be a medium of exchange. Also related to children was speculation as to whether babies and children who had died would be resurrected as babies and children or as adults.
Another wacky one was that, eventually, there would be no more children. At some point, the earth would be "full" and no more children would be born. I never heard the one about populating other planets; I thought that one was exclusive to Mormons.