Hit the green flag and let your device lag! Trust me, you don't want to see the lag counter hit more than a hundred thousand- Test the machine by letting it run in the background while you do something else online (like play another Scratch game). WARNING: DON'T USE FULLSCREEN UNLESS YOU THINK YOUR DEVICE WILL BE ABLE TO HANDLE IT.
Maximum lag that I could achieve was ~2 fps No literally... 2 FRAMES PER SECOND WITH ~10000 GOOFY AH CLONES.