A lot of the more lighthearted stripe of science fiction tends to portray Earth as a galactic backwater, yet still features aliens who are fans of – or at least aware of – Earth media.
The thing is, if Earth is really such a backwater, even our most popular media franchises must be incredibly obscure by the standards of galactic civilisation.
An alien dropping a Star Wars quote would be like an American dropping a reference to an anime film that was released direct-to-LaserVision in 1982 and has never been localised in English and expecting to be understood.
In other words, these aliens must be massive dweebs.