we once had a passenger come down to the aft galley during a back of the clock all in a huff, telling us there is a strange light on the end of the wing. we informed him that was the light on the wingtip, to which he replied "i think there may be a fire". two of us went into the cabin to investigate (A320 galley windows do nothing...) and looked out the pax windows, looked at each other, and said: "sir, that's the moon"...