One fan at a Willie Nelson concert was clearly moved by the experience -- and, according to YouTube commentators, possibly by an illegal substance as well.

In the video (shown above), the man can be seen dancing as if he was the only person in the room. Clearly enjoying himself, he didn't seem to pose a threat to himself or others, so concert attendees and security left him alone, although they did give him plenty of room to show off his moves.

Many of the comments on the video indicate that the dancing man was on drugs of some kind, with guesses ranging from marijuana to "molly," the crystal form of the hallucinogen MDMA which is popular at music festivals. Whatever he did or didn't ingest, the result is a viral video classic.

The clip was posted online in July of 2012, and it's been viewed more than 315,000 times since.

As for Nelson, the 'On the Road Again' singer is indeed on the road again, following a short hiatus due to a shoulder injury. He appeared at the Zac Brown Band's recent Southern Ground Music & Food Festival in Nashville, Tenn., and will next play in Louisville, Ky. See all of his upcoming shows here.