Scared of the Dark?!?!?!

What age do children normally act scared of the dark? I remember babysitting when I was younger and thinking it was so silly when parents would say "We leave their (the child's)  door open with the bathroom/hall light on." Really? But alas, the last couple nights Oliver has pleaded, with every ounce of his little toddler self, that we keep the "light on", "light on" and "door open." Where did this come from? He's been sleeping in the dark with the door closed for almost two years now. Alone. Not in bed with us. Is it that he's scared of the dark? Or maybe that little man is scheming for a way to still participate in family goings on and he can hear and see better with the door open and the bathroom light on? Regardless, I take back thinking it was silly. It's really not that big of a deal. As long as he's sleeping in his own bed and falls asleep on his own, I'm good. Maybe it's Monster's Inc that freaking him out???

The crazy thing about this kid is that once he's fast asleep you can turn on his bedroom light and change his diaper without him waking up.