How do I implement youtube video in game

is there some logic to implement video in background or as a part of scene in layout

and

also

to be activated by some event

That's a good question. I would also like the answer. But to expand on the question: since I'm going to have a huge world, and it's all side scrolling, and space is limited, is it possible to advertise throughout the world using a billboard style thing built into the game instead of an ugly bar across the bottom?