Have you ever met someone who looks like you or does similar things? Moments like these are funny. For instance...
My friend sits behind me in a class. With an intensely slow and uncaring teacher. So on one of those days where he decides not to teach us anything, (it seriously coud have been ANY day), I was just sitting there, chin in hand, tapping my pen on the table. My other friend noticed that behind me, my friend was in the same position, but clicking his pen's tip in and out.
Later that day, in P.E., I was standing around. Nothing was really happening, so I pulled a couple of paper clips out of my pocket and started playing with them. My friend was behind me again, doing the exact same thing. It was weird, we didn't even notice.