That might have been because Harris was disguised as Jurgen Vollmer, the host of The Voice Austria. And he spoke with a thick Austrian accent.
It was all part of the premiere episode of Harris' new show Best Time Ever, so this Harris/Vollmer character did some awkward behind-the-scenes interviews with the coaches, and Shelton didn't seem very enthusiastic.
"I have no (expletive) clue what we're doing out here," he said to Adam Levine before the interview, and after it, he just asked, "What the (expletive) just happened?"
Then Shelton was left kind of speechless when Harris/Vollmer told him and Levine that they were both his favorite coaches.
When Harris/Vollmer does his blind audition with "And I am Telling You I'm Not Going" from the Broadway Musical Dreamgirls, Shelton was ready with his hand hovering over his button because he said he could already tell this was a good one. But none of the coaches turned their chairs around.