The coaches teased Adam Levine about his new hair color, inviting comparisons to Miley Cyrus and a futuristic cyborg.
"I don't have an explanation," PEOPLE's Sexiest Man Alive defended of his new coif. "I woke up. I had the day off and I thought I'd look like Shakira. My mom hates it. I kind of felt like that would happen.
Shelton, who last week Tweeted Levine's private phone number, could not resist the moment. "That's Adam? I thought Meg Ryan was sitting in with us tonight for a second there."
The Voice introduced its two newest coaches – Pharrell Williams and Gwen Stefani, who teamed up to perform "Hollaback Girl" – on Monday night as the eight remaining artists performed.