This happened to me on a flight from LHR. I had the aisle seat and sitting in the window seat was a young person maybe 11 or 12 years old. After about three hours of flying, I asked him if he was traveling alone and he said "I have people on the plane." Well, his "people" did not make an appearance for the entire 8 hour flight and this child was understandably bored. The entertainment system was malfunctioning so he entertained himself by raising and lowering the window shade repeatedly as well as the tray table. He did some singing and talking to himself. The plane was full so I couldn't change seats. At one point, I went all the way to back of the plane to use the toilet, came back, buckled in and closed my eyes. I felt a tap on my arm and he said "I need to go to the bathroom." Sigh. Seat belt comes back off. He did try to sleep at one point which was awesome except that he angled himself in such a way that his legs were in my under seat space. I actually felt sorry for him that nobody came to check on him for the entire flight.