I've taken classes on C++ and C# programming languages.
I can honestly tell you that sure it wouldn't be difficult to program, but it would just take too much time. Basically, he'd have to seperate everything that had to be affected into seperate images: each individual difficulty box, the red outline; and for the roster: the hand, the selector circle, each individual character box (only a few for "leaked" video), and the character display. Then somehow they animated the screen before the battle with link, they had to animate it somehow. Also, I just noticed that he puts the cursor hand over the character pic to change colors, it's weird that he'd put the cursor over unless it's fake, but also why program it if it's not important and really fake. He also had to animate to bar that comes across saying its ready to begin. This would be a long process, and it seems like he's done some things you wouldn't necessarily have to do if it was a fake. If it is a fake he put a lot of effort into it, almost too much, which makes me think it's real. He also somehow got a Japanese clip of Pit saying something, I can't here him and don't know that much Japanese, but that'd be very hard to get a sample of, maybe from Whobby. It's a hard call to make.
This newest one would be pretty easy, and almost makes his credibility go down. I also think that maybe in Japan they aren't caring about spoilers as much, maybe they just don't show excitment the same way, or maybe he doesn't put that much effort into recording it since Japan gets it so soon, and the Japanese may not have a demand for this type of thing.
This whole "leak" thing makes me want to try to replicate these just to show how hard, easy, practical, or likely it would be.