I was skeptical when I heard about this--but I "fell" for it. Researchers at Caltech came up with an optical illusion that relies on sound to make you see something that isn't really there. Try it:
Did it work on you?
Their full description:
"Caltech researchers have developed these two new illusions that reveal how the senses can influence each other—in particular, how sound can give rise to visual illusions. These illusions occur so quickly that they illustrate a phenomenon called postdiction (as opposed to prediction) in which a stimulus that occurs later can retroactively affect our perceptions of an earlier event."
I'm still not sure I buy the "postdiction" part, as I feel I perceived the illusion in real time. You?