fanwink

When the writers of a television show, movie, video game or other product include jokes that the audience will get based not on the show, but on outside knowledge. Actors meeting co-stars from previous series, saying famous lines, or put in familiar situations just to play to the base like an asexual form of fanservice.

An in-jokey shout out in a body of work. The type of thing that fans will catch, but everyone else will ignore. More obscure than a simple reference, more in-depth than an in-joke, but a unique kind of thing anyway.

The writers are, in effect, winking at their fans. Fankwink.