This really happened to a colleague of mine when he was in the infantry. He was assigned to teach A., a new and not-too-bright soldier how to navigate by finding the North Star. He did his best, but he could see it wasn't getting through, so he just hoped no-one would test the new guy. A couple of weeks later, during a long march by night, the sergeant remembers that A. wasn't tested yet. So he halts the platoon and asks, "Private A., where's the North Star?" Private A. looks hard at the sky for a long time, and finally declares, "We've already passed it, sergeant!"
(From the "Rest" of RHF)