Larry Butler's the third wheel who joins Roy and Jillian for their daring trek up Devils Tower. Like them, he's been plagued by visions of a mountain, resulting in an incessant urge to doodle it. Out of shape, he's unable to keep up with Roy and Jillian during the uphill portions of the hike. This lets the military helicopters catch up with him and douse him with E-Z-four.
He shouts, "Los Angeles!" just before the E-Z-four knocks him out. It's probably a joke about the air quality in L.A., which another person in the helicopter had just compared unfavorably to the (supposedly) toxic air at Devils Tower. It's a great last line.