Several authors create works in more than one genre. Some use many, some like to mix it up so much that their work isn't recognizable as any genre, and some like to keep the elements of the genres they're using separate, but all of them like to mix together genres, reasoning that if a story in one genre is good, a story in two or more genres must be better.
This is such a well-established tradition that some genre mixes inevitably become established genres in and of themselves. These are Hybrid Genres: genres that blend themes from two or more parent genres.
See also Genre Mashup (when an individual work combines multiple genres while not necessarily creating its own genre.)
Examples:
Fiction Genres- Action Horror (Action and Horror)
- Alternate History (Historical Fiction and Speculative Fiction)
- Bromantic Comedy (Buddy Picture and Romantic Comedy)
- Capepunk (Superhero and Punk Punk)
- Cattle Punk (The Western and Punk Punk, usually Steampunk)
- Comic Fantasy (Comic Literature and Fantasy)
- Dark Fantasy (Fantasy and Horror)
- Dramedy (Comedy and Drama)
- Dungeon Punk (Fantasy and Punk Punk)
- Fantastic Comedy (Comedy and Speculative Fiction)
- Fantastic Noir (Speculative Fiction and Film Noir)
- Gaslamp Fantasy (Fantasy and Steampunk)
- Gothic Punk (Gothic Horror and Punk Punk)
- Historical Detective Fiction (Historical Fiction and Mystery Fiction)
- Historical Fantasy (Historical Fiction and Fantasy)
- Horror Comedy (Comedy and Horror)
- Military Science Fiction (Military Fiction and Science Fiction)
- Ocean Punk (Wooden Ships and Iron Men and Punk Punk)
- Panty Fighter (Fighting Series and Ecchi)
- Paranormal Investigation (Speculative Fiction and Mystery)
- Paranormal Romance (Romance and Speculative Fiction)
- Real Robot Genre (Mecha Show and Military Fiction)
- Romantic Comedy (Romance and Comedy)
- Samurai Cowboy (Jidaigeki and The Western)
- Science Fantasy (Science Fiction and Fantasy)
- Sci-Fi Horror (Science Fiction and Horror)
- Space Western (Science Fiction and The Western)
- Speculative Documentary (Speculative Fiction and Documentary)
- Superhero Horror (Superhero and Horror)
- Supernatural Soap Opera (Speculative Fiction and Soap Opera)
- Super Robot Genre (Mecha Show and Superhero Stories)
- Weird West (The Western and Supernatural Fiction)
Music Genres
- Bossa Nova (Samba and Jazz)
- Country Rap (Country Music and Hip-Hop)
- Electro Swing (Jazz and Electronic Music)
- Dark Cabaret (circus/fairground music, traditional instruments and Punk, Goth Rock, or Dark Wave)
- Dark Wave (Synth-Pop and Goth Rock)
- Folk Metal (Folk Music and Heavy Metal)
- Industrial Metal (Industrial and Heavy Metal)
- Jazz Fusion (Jazz and Rock)
- Jazz Rap (Jazz and Hip-Hop)
- Pop Punk (Punk Rock and Pop)
- Progressive Metal (Progressive Rock and Heavy Metal)
- Rap Rock (Rock and Hip-Hop)
- Ska Punk (Ska and Pop Punk)
- Symphonic Metal (Classical Music and Heavy Metal)
Video Game Genres
- Action-Adventure (Action Game and Adventure Game)
- Action RPG (Action Game and Role-Playing Game)
- Action RTS (Action Game and Real-Time Strategy)
- Dating Sim (Romance Game and Simulation Game)
- Explorer Horror (Horror Video Games and Adventure Game)
- Platform Fighter (Platform Game and Fighting Game)
- Puzzle Platformer (Puzzle Game and Platform Game)
- Run-and-Gun (Platform Game and Shoot 'Em Up)
- Strategy RPG (Strategy Game and Role-Playing Game)