Free power for the rest of your life! What manner of sorcery can this be? This video will set someone up for two possible kinds of rude shock: dangerous and disappointing. How do you think this was done? -via The Daily What
Once the power strip is "energized" you never the whole thing in frame. Their is a coil of wires on one side which could be an illusion to make you think that it's plugged into itself but the edge of the cable is out of frame so you can't tell. The camera switches angles and the other side of the strip is now out of frame.
A part of the power strip is always out of the shot when it is "powering devices."