- The Tralfamadorians have five sexes that are all necessary to make babies.
- They all look the same to Billy, though, because their sexual differences are in the fourth dimension.
- The Tralfamadorians tell Billy that they have observed seven sex differences in Earth humans.
- Billy has absolutely no idea what five of those seven sex differences could be, since they're in the fourth dimension.
- The Tralfamadorians try to explain, but Billy doesn't get it.