Throwaway line
In comedy, a throwaway line is a joke delivered "in passing" without being the punch line to a comedy routine, part of the to another joke, or there to advance a story or develop a character. Throwaway lines are often one-liners, or in-jokes, and often delivered in a deadpan manner.
In comic strips throwaway gags are often placed in the throwaway panels of the comic, and are located there so that removing the throwaway panels for space reasons will not destroy the narrative of the central comic.
In episodic fiction, a line intended originally as a throwaway line in one episode may later be retconned by being incorporated into the back-story of the main drama, and used to develop the longer-term plot. As an example, in the second season of Breaking Bad, the character Saul Goodman, threatened at gunpoint by Walter White and Jesse Pinkman, not knowing who they are as they are masked, and not yet knowing what this is about, tries to defuse the situation by blaming a guy named Ignacio, who is never mentioned again; however, the character Ignacio is introduced in the second episode of the prequel series Better Call Saul, produced several years later.
