Crazy video editing

I saw some of that Big Live Live Show, Live! test footage (A part of me thinks it's crazy that I watched a video of a dude in front of a green screen with no sound for several minutes) and I was wondering how they were doing all that crazy on-the-fly chroma keying, transitions and all the other fancy stuff they were doing. 
 
I don't know much about video production but this has piqued my interest so anyone have any ideas?

they have people already making the things that they want. they just add it in while they are going a long.

Test Footage?  Where?