One of the most basic expectations of shooting a film is that actors hit their markers and do what is asked of them, all while being aware of the camera's presence.
When directors call "action," it's game on until they yell "cut!," and actors have a window of time to deliver their lines and maybe, depending on the director, experiment around a little.
But all filmmakers have their quirks, and some have seemingly gotten a kick out of shooting actors without their knowledge.
Perhaps this has been in an attempt to elicit a more naturalistic performance from a "stolen" moment, or simply a result of a director's idiosyncratic working methods, where they maybe don't even call for action or cut.
In these 10 iconic and beloved films, these actors weren't aware of the shooting situation in at least one scene, the director instead surreptitiously capturing them on-camera through trickery and deceit.
In most cases you'd never have any idea from the end result, all of which seem like well-trained feats of naturalistic acting - as just might be the point.
You can't blame these actors if they got a little peeved at having a performance teased out of them in such a way, but the results surely speak for themselves...
10. Michael Douglas - Traffic
Mid-way through Steven Soderbergh's Oscar-winning drama Traffic, the U.S. President's drug czar Robert Wakefield (Michael Douglas) heads to the U.S./Mexico border in California, where he speaks with a U.S. Customs Service official while observing inspections of cars crossing the border.
The scene has all the gritty authenticity of reality, and that's because it basically was.
Soderbergh took Douglas to the actual border and had him meet with real U.S. Customs Service executive Rudy M. Camacho.
This wasn't originally intended to be part of the film, but sensing worthwhile material on the horizon, the director quietly began filming the exchange with a small handheld camera without notifying Douglas.
This explains why the video quality looks markedly less-clear than the rest of the film - the garish, overexposed lighting suggests that Soderbergh basically just pointed his camera and shot without setting the scene up as usual.
Similarly, the audio quality is of much lower quality than in other scenes.
Soderbergh reportedly hoped that Camacho wouldn't render the material unusable by referring to Douglas by his real name which, thankfully, he didn't.