Since it's on youtube we are already suspect of anything they happen to show. there's also the title of the video. some part of us knows that it's probably fake.
These people are coming in expecting an interview and have no reason to think otherwise. They aren't on their guard for pranks so when this happens and the other person in the room sells the prank... you can't help but fall for it.
The other thing to note is that we're seeing it through a camera whereas they are really there. Some TVs out there really do look like windows that you could reach through and touch people. They also kill movies for me because of the super realism. I can see makeup lines, edges of prosthetics, etc.
