Post-It notes are a pretty unassuming form of communication. Sure, they can serve as persuasive reminders to fax that memo or pick up some milk, but as eerie messages from the undead? You'd probably expect ghosts to get in touch through other means, like blood on the walls or ear-splitting shrieks. I Thought I Told You to Wait in the Car blogger Richard Vivmeister Hirst (a self-described "human man" from Preston, England) was haunted by a Post-It-leaving spirit who sent him spooky and annoying messages like a passive-agressive roommate from the beyond.