You probably already know what you need to do to pull this prank just from reading the title. That’s right, take your victim’s toothbrush, wet it, and then smear the bristles with a ton of table salt. The next time your buddy goes to brush his teeth; he won’t know what hit him. Just make sure you get the right toothbrush and not your friend’s girlfriend’s toothbrush as my friends did. She was pissed at them for 3 weeks and I think deep down just as pissed at me for having such dumbass friends.
I have contemplated smearing a friend’s toothbrush with hot peppers or a hot pepper extract instead of salt. Can you imagine the pain? They may at first think to themselves, “Wow, this new toothpaste has a little bite to it, I guess that’s how you can tell its working.” Only minutes later they will find out they are in for a world of hurt until the swelling goes down the next morning.