This app can quickly rename all of a phone's contact to a joke like "Nicolas Cage" or "Batman". The idea is that if your friend's phone is unattended, you can download this app, mess with all their contacts quickly, and put the phone back.
And yes, the app can undo the damage it causes. :P
25,000+ installs on Google Play
For more of the story behind this app, check out the comments! 3 years ago