Take one existing show genre, add another, and presto! you've got a brand-new genre.
The most famous example is
Star Trek: The Original Series, pitched as a
Wagon Train to the Stars (
The Western +
Space Opera).
See also
X Meets Y (for when it's works, not genres/tropes) and
Recycled In SPACE (for when it's a work plus a genre or tropes). Compare and contrast
Genre Busting.
Examples:
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Anime and Manga
Comic Books
Film
Literature
Live Action TV
Music
Video Games
Webcomics
Web Original