How did they do that shit? I would do that to my friends cars in a heartbeat!!! Just to piss them off!

 

that was pretty good lol haha

 

You could do it with a full throttle switch used for nitrous applications.Buy one of those for like a dollar then some wire and run the wire from that switch to the horn somewher(splice) then make the switch click on and off when the brake is applied by puttin the switch behind the pedal on the firewalla somewhere.Thats probly not how they did it but its for sure to work