Here’s a quick explanation on why this is just a trick and not a skill of tying shoe laces.

Watch the video first ..

http://www.youtube.com/watch?v=dSrcLz4gqMY

and now see what he did it.

1.

See how his pant is covering the actual laces that are tied.
The ones marked in red are  tied from inside which he pulls up when he shakes his leg.

2.

Pulls his pant up along with the laces that were hanging out(circled in red).

3. 

Check the red line. He has pulled up his pant to show the tied laces and pulled up the dangling laces.

Neat trick I’d say.