I would be freaked out if simba started meowing at nothing, he does sit and stare for ages at the ceiling though, or anything high up , he just wants to get up there!
Mine is very quiet, so she just stares at the cieling. We've got mice in there, and she can hear them running around. She's caught a frightening amount of them in the last two months...she never kills them, just holds them and calls me, gives me a rousing game of tag, then gives me the mice in exchange for treats....