As agreeable as it is insidious, Morgan Spurlock’s latest exposé of corporate control via immersive humiliation is his best, most formally inventive project yet. The premise is initially fuzzy—Spurlock proposes to fund a doc about product placement solely with product placements—and The Greatest Movie Ever Sold bogs down early with a headache-inducing parade of brand advisers, spinners, massagers, and mediators with whom he consults. Once he sits down with the marketing teams from various would-be sponsors, however, the movie kicks in. Their desperation is as plain as our susceptibility is alarming—something a detour to São Paulo, Brazil, where outdoor advertising is illegal, makes painfully clear: The city’s bare walls and billboard-free highways seem disturbingly naked. Spurlock’s customary half-assed musings over how all this might affect him don’t detract from the horrible fascination of watching him become a consummate pitchman for his art. He subtly sells something to everyone he encounters, from rockers OK Go (who contribute an OK closing tune) to Ralph Nader (all too easily intrigued by Morgan’s Merrell slip-ons) to those of us gaping in the audience. One wag dubs the experience “pleasingly circular,” but it’s more like watching a beloved pet devour itself tail-first, deliberately and with alarming grace.