It's fake, but it's still funny.
Update: I thought this video was real at first. Turns out this video isn't real (no matter how much I wanted it to be). Meleny pointed out a few reasons why it's fake in the comments section. Adding to that the fact that there are secret service men all around Bush at all times. I think someone would have said something, including the interviewer. Plus, as soon as Bush found out about it, he would have had the video destroyed immediately! I checked ABC's The Early Show's website and saw nothing about it. Also, The Daily Show would have been all over this! Someone said it was a spoof that came from either The Tonight Show or The Jimmy Kimmel show, but the video shows the title of a site called TheYNC.com, which is a porn site (as Meleny said).
Damn. If this video was real, it would have made my whole week better. :)
Look in the background behind Bush's head while he's talking.