Two-faced

I'm not sure if this is real, I just heard it somewhere. A parent was walking along with his young son and happened to bump into a neighbour. The little boy kept staring at the neighbour and tried to look at the back of the neighbour's head. The neighbour was perplexed and asked the young boy "Are you OK little one?Is something wrong?"

The little boy frowned and replied: "My dad said you have two faces but I can't see the other one."