What are they? Well, the first answer is "not real," obviously, but the second answer, and the one I'm going with today, is that ghosts are dicks. They are. When have you ever seen a nice ghost in a movie? That's right, almost never. 99% of those fuckers (the other 1% are Casper and that bathroom pervert ghost in Harry Potter) just go around revenge-killing people who usually aren't even tangentially related to the ghost's grisly fate, because that's how revenge works in horror movies; someone dies in 1407 and then they spend the next two hours of your life creatively murdering teenagers whose only hobbies are making bad sex puns and canoeing.
But what if ghosts were real, and not just a figment of part-time plumbers' imaginations? What would they be like?
I know what I'd be like.
Not the murderous kind of dick; just the change-your-tv-channel-to-BET-and-never-let-you-change-it-back kind of dick. The knocking things off shelves kind of dick. The flicking you in the back of the head while you shower kind of dick. Imagine if in Poltergeist, the house had been built on a 90's teen sitcom graveyard instead of a native american one, and you'll get the idea. I'm talkin' pranks, here; pranks of the highest order. Best part is, I'd be safe from any and all possible retribution on account of being, y'know, intangible. Incorporeality--not incorporealty, that's a catchy name for why the housing bubble popped--would be the ultimate get-out-of-anything-free card; I could spread peanut butter on every inch of someone's bed and they couldn't do anything, because fuck you, I'm a ghost, what are you gonna do, take me to ghost jail? I've got something better than diplomatic immunity, assholes!
Once in awhile I'd be nice to the people who I'd decided to torture for the entirety of their mortal existence, of course. Leave 'em some flowers. Peel their carrots for a salad. Of course, to them, the magical self-peeling carrots would be absolutely fucking terrifying and the flowers would merely imply they're being stalked, but that just enhances the fun. Gotta sprinkle some laxative into the cupcakes, too, of course...
Now, you might be thinking that I'm kind of a bad person. You wouldn't take advantage of your complete immunity to all retribution; you'd be a nice ghost. But would you really? As an old saying goes, "absolute power corrupts absolutely," and I'm absolutely sure that even the most auspiciously altruistic among us would fall prey to the allure of a little mischief. Maybe that's how the horror movie ghosts started out, you know? First you put saran wrap on the seat, next week you're eating their ear; it's a slippery slope. If it happened to Mike Tyson, it can happen to you.