Wikipedia
Meta-reference
Meta-reference, a metafiction technique, is a situation in a work of fiction whereby characters display an awareness that they are in such a work, such as a film, television show or book, and possibly that they are being observed by an audience. Sometimes it may even just be a form of editing or film-making technique that comments on the programme/film/book itself.
When used in a work mostly using a regular setting, it is often referred to as "breaking the fourth wall".