My kids do this all the time until your ears bleed if you pay too much attention. When Avatar became popular, my son watched it every afternoon after schooling for around two weeks straight. He did the same for Iron Man II for around a week.
We let him do it. But we preselect the videos he watches, just to make sure he doesn't imitate something out of bounds. But whatever he watches, parental guidance is always necessary. I mean, always. He talks about the movies before sleeping and I make sure I listen just to make sure I see what he's thinking. Then as a father, I would guide him.