Chekhov's gun

a plot device where what is to come is hinted at, to arouse interest or to guard against disappointment

a plot motivator that is necessary to the plot and the motivation of the characters, but insignificant, unimportant, or irrelevant in itself

drawing attention to a certain element to mislead

a long-winded anecdote designed to lure the audience into a false sense of expectation, only to disappoint them with an anticlimactic ending or punchline