The 56-year-old "You're Gonna Miss This" singer, a longtime friend of Shelton's, had the Coach in stitches with his signature dry humor while serving as a mentor on this season of The Voice. In ET's exclusive blooper reel from the battle rounds, Adkins takes Shelton to task over his "horror show" dance moves, prompting Shelton to reveal his secret nickname: "Shufflin' Shelton!"
Elsewhere in the outtakes, Kelly Clarkson and Hailee Steinfeld joke about their larger-than-life pipes, Alicia Keys and Shawn Mendes get a lesson in warm-ups and Adam Levine takes some fresh ribbing for his wardrobe. See the exclusive clip in ET's player, above!
Behind the Scenes of 'The Voice' With Alicia Keys and Adviser Shawn Mendes (Exclusive)
"I was like, I feel like I should be getting in front of the microphone and singing, and asking her for advice," Mendes told ET. "I think there was one moment that I was sitting there halfway through a song and I'm like, 'Am I really sitting here right now with her being an adviser? I'm 19 years old!' So this is really crazy."
For more behind the scenes action, watch below. The Voice airs Mondays and Tuesdays on NBC.