Once you’re aware of the concept of Chekhov’s gun, you start to instinctively spot devices that are meant to be called back later in the script and subconsciously anticipate them, making it a Pavlov-Chekhov gun.

But if the initial introduction of the Pavlov-Chekhov gun is too forced/obvious, you might feel compelled to turn off such a predictable movie before the device is recalled and you’ll never know if it was actually brought back. Maybe it was, maybe it wasn’t, maybe it exists in an unobserved quantum state… a Schrödinger-Pavlov-Chekhov gun.