I remember once hearing somebody in the film industry use a term for a brief early scene or shot that marked out that a film would be part of the science fiction. For example, the films Predator (1987) and The Thing (1982) both have opening establishing shots of alien spacecraft, which confirm for the viewer that the films—which both start out with apparently realistic events—will eventually turn out to be science fiction.
The specific example where I encountered the term was in a discussion of science fiction filmmaking, but it the term might or might not be used more widely to indicate other speculative fiction genres. I wanted to know what this term, since it seemed useful for discussions of the framing of these kinds of films. The term I am trying to remember might have included "shot" as part of the name, but was something more specific than the well-known "establishing shot," which is a (usually) wide shot used for setting the stage and context for what is to follow.