This prank is hilarious it will make your friends phone go crazy but it dose not do any real damage so completely safe.
Check this video out you will understand what it dose.full tutorial in the video.
Step 1: Developer Option
Go to settings then scroll down to developers option click it.
Then activate the developers option.
Step 2: Real Thing
Scroll down below drawing there will be a option show surface updates click the check box and then relax its done. Screen will go crazy make it look like a virus
Step 3: Safe
Developer option is made maily for programmers for testing device just turn off developer option to bring back device to normal