I was wondering who that guy was

Foo Fighters Joined By Unknown Man In Grammy Acceptance
The Foo Fighters won the best hard rock performance Grammy, but the most interesting part of the honor came just after their name was called. While singer-guitarist Dave Grohl and drummer Taylor Hawkins were at the podium making their acceptance speech, a large, unidentified man was standing behind them cracking his knuckles and waving to the audience.
As Grohl appeared to end his thank you speech, the man leaned into the microphone to comment.
“And rock would not be anything without B.B. King,” the unknown man said. “Rock would be nothing without him. Thank you.” Grohl responded, “I was gonna, I was gonna say that.”
Backstage after the incident, Grohl and Hawkins were still perplexed about the interruption. “He just wanted to go to the bathroom, because after that whole schlemiel he stepped out in the backstage and said, ‘I gotta take a piss.’ That was it. I don’t know,” Grohl said about the unidentified man. Hawkins added, “Does anybody know who that dude was? No. I have no idea…Yeah, he’s our DJ. He’s our MC.”