Not bothered by the request, Mac happily responded, "What song do you want to play?" before inviting the kid on stage and handing him his guitar.
When the song kicks in at the 1:50 mark and the fan perfectly fills in for Mac, a giant smile takes over DeMarco's face and the crowd rallies behind the kid. Or, as all the YouTube commenters on the video put it: "Hey kid leave some pussy for the rest of us" and "This kid fucks."
By the end of the song, Mac is swinging his microphone over his head and the kid gets a roaring ovation. Beautiful. Watch the clip above.