Macon Blair’s spiritually minded and drug-fueled road trip film The Shitheads is never as funny as it thinks it is. Like a flashing engine light in your car that you keep trying to ignore until the next oil change, it is so high on its own supply, and so admirably and foolishly sure of its own capacity to entertain, that it lacks a critical self-awareness of when its sensibilities have run their course. It’s certainly unpredictable and will surprise some viewers through its narrative choices and metaphysical provocations, but it's all for a shallow purpose, as if it were propelled only by its tendency to zig where others might expect it to zag.