The lawnmower one isn't funny. That happened to a good friend of mine when she was a little girl, and she's lived with prosthetic legs since then. So don't laugh at that, please because she is such a happy energetic girl that it would break my heart.
I loved this because Arthur, when he and Merlin are alone together, always throws stuff at Merlin or teases him. But when Uther walked in it was like, "Oops! We were acting like two little boys and Dad caught us.