Multiply People in Adobe AfterEffects

Hi, This video and tutorial was made a while ago, while the harlem shake was still "popular" 
I did this video for some friends party, the problem was they were not with a lot, so I had to do some postproduction to make the video 
"Crazier".

This is not a step by step tutorial but more of a workflow to give you an idea on how to work, to do something like this. 
You'll need some basic editing skills to do something like this
Hope you like it and feel free to comment ;)