Not on UA (a domestic Chinese flight) but this guy was the worst - I think he was non-rev. I was one of the first to board this 7am flight, and he was already there, seat nearly flat, tray table out with food and drinks. This guy must be connected to the airlines, as FAs bent over backward and served to his every need, and took his unreasonable demands. Finally, an attentive FA helped move his seat to the sitting position as we taxied and lined up for take off. Not even a minute after in the air, he's back in the sleeping position, and finally the whole episode repeated when we landed. I would have removed him if I was the working for the airlines.