Prank 3: Phone Panic
If your colleague uses a corded landline phone, this one’s for him. When he’s not at his desk, unplug the cord from the handset and tuck the loose end neatly into the coil or somewhere discreet on the main device. Wait for him to return, and then ring his phone. He’ll panic when he doesn’t hear any sound on the receiver, and struggle for a bit trying to fix the phone.