What happens when you drop acid in Yosemite and discover a giant double rainbow. Probably something that resembles this reaction. For the record, Paul Vasquez, the happy soul that shot this video says he was completely sober at the time and simply high on rainbow power.

The other possibility is this guy is pulling an Andy Kaufman and just getting really deep into his character "Hungry Bear". Whatever the case may be it's still pretty funny.  "That's so intense".