WATCH: The Coaches From “The Voice” Cover Each Others Hit Song in The Premier of Season 9 – Plus See Neil Patrick Harris Prank The Coaches [VIDEO]

Get ready for the live performances, spinning chairs and... a bromance.

Season 9 of NBC's "The Voice" returns Monday, September 21 at 7:00 (central time) with coaches Blake Shelton, Gwen Stefani, Pharrell Williams and Adam Levine.

Strange things happen this season, including Neil Patrick Harris going undercover on The Voice to promote his new show, "Best Time Ever".