Riff Raff is the self-made rap star signed to Diplo's Mad Decent label and still embroiled in very real beef with actor James Franco and his role of "Alien" in the movie Spring Breakers, which Riff Raff says is a direct rip-off of his persona.

These unlikely allies have come together with Riff Raff joining the Neighbourhood as a new band member. The union was made official onstage during the 24th Annual KROQ Almost Acoustic Christmas show at the Shrine Auditorium in Los Angeles Sunday night (Dec. 8).

"It's kind of the evolution," Rutherford said during an interview with KROQ (a Radio.com station) after the show. "[Riff Raff] gives some contrast to the Neighbourhood."

The new union was announced while the Neighbourhood was performing the single "Sweater Weather," which has dominated the airwaves and playlists since its release in earlier this year. Riff Raff appeared onstage and added vocals to an extended version of the song.