Avid movie watchers may already know, but Apple has a "villain clause." This means that they will allow films and television shows to use their products but with one condition: villains are not allowed to use them.

Johnson thought twice about sharing this information, with fears it could ruin his next mystery movie.

Speaking to Vanity Fair, Johnson explained the clause: "Apple, they let you use iPhones in movies, but – and this is very pivotal – if you're ever watching a mystery movie, bad guys cannot have iPhones on camera.

"Every single filmmaker who has a bad guy in their movie that's supposed to be a secret wants to murder me right now."

In the first Knives Out film, every suspect in the murder mystery used an iPhone at some point, except for the actual killer.

Some eagle-eyed viewers did notice that in the Knives Out sequel, Glass Onion, none of the characters used Apple devices.

Although the villain clause is not stated in Apple's official guidelines, there are caveats on how the devices can be used in promotions or advertising.

"The Apple product is shown only in the best light, in a manner or context that reflects favourably on the Apple products and on Apple Inc," the guidelines read.