The boy sent me this Wikipedia article about vampire watermelons. I was very skeptical, and there's always a chance that upon revisiting the site I'll find it's been 'corrected'. But if it's true, then isn't it fascinating! According to the article, it's an old Romanian thing which also applies to pumpkins and anything else left outside after around Halloween. Halloween pumpkins would certainly make more sense, knowing this. But watermelons? Apparently they aren't too scary to Romanian folk because watermelons don't have teeth.
One of my co-workers has a spider phobia - this explained why she sent a library patron to me, to colour photocopy some pictures of spiders. But the amusing thing was that she felt compelled to wash her hands after having to handle some books on the subject. (We all know books are great germ-carriers anyway, so it wasn't wasted effort.)