Film vs DigitalFilm: As many de-bunkers have explained.
The processing can cause strange images to appear, as well as light getting into the camera from either a defective door or perhaps accidental opening.
Other issues can be, incorrect loading of film, old and or defective film (I assume this could also apply to Polaroid film) and camera malfunctions causing double exposures.
Both film and digital are subject to lens flare.
Digital: Some explanations I have read were.
The proximity of flash to lens, causing "orbs".
Lack of circular polarizing lens. (true not everyone thinks to use one with digital.)
The extreme sensitivity of digital, allowing more light than even the human eye of the operator is able to detect.
Bugs and water vapor causing orbs, streaking and fog like ghost images.
Who's to say that a digital can't become subject to double exposure, say a defective spot on the memory card.
Every 730th image, there's aunt Mabel, an orb or strange fog.
With so many ways to explain how an image can show up, how can any photographs even be considered "real"?
What do you use?
Do you find it reliable?