My son is 18 months old. Today, we were in Boston to go to a doctor's appointment so we had dinner out there. We're at the food court, and we were the only ones in our section. My son then turned away from us and was talking (or trying to talk because he can't really talk) to an empty section next to us. I mean there weren't any tables or chairs where he was talking. Then he started to nod his head and tried to hand over an apple slice and said "apppp?" which is his way of saying apple. My question is, is he too young to have an imaginary friend? What should I do? Should I bring it up to his pediatrician or just brush it aside?