First off these codes were not made by me,i just got the cheat file from this thread at the MKW site,i just went through the codes to get it working properly,so first of all go to this thread at the MKW http://www.mortalkombatonline.com/content/forum/showmessage.cds?id=46041 and got and get the latest cheat file released.
Right first off get UMK3 up and running,then enter into the cheat menu and set the kombat zone to the pit 3 like so



then scroll down and set the first of the invisible lifebar cheats to on like so



then scroll down again and set the 4TH sprite and background ripper,it has to be the 4th or the game will reset itself when you try and get the get hit sprites



Finally scroll down again and turn the background to the purplish pink color like so



Now start the game as normal and you should get something like this.



again these are not my codes,i just thought id post this up so people could rip UMK3 sprites easier.