What does “le falta un tornillo” mean in Spanish?

Le falta un tornillo, “a screw is missing from him,” is Spanish’s version of “he has a screw loose” — describing someone acting strange, illogical, or a little unhinged, as if a small missing part explains it. This clip sets up a pun on exactly that image: someone asks tienes vértigo? (do you have vertigo, dizziness that makes things look crooked?), only for the real answer to be an actual, literal tornillo that fell off something nearby.

The expression is thought to date back to the Industrial Revolution, when machines were new enough that a missing screw was a believable, concrete explanation for something malfunctioning — the same logic later applied to people. It’s mild and often affectionate, more of a “you’re a little nuts” among friends than a real insult, much like English “screw loose” or “a few bricks short of a load.”