World's Greatest Dad, Bobcat Goldthwait's latest garishly potty-mouthed and over-the-top black comedy, blows up every rule of taste, good cinema, and common sense, and somehow gets away with it. Robin Williams plays a high school poetry teacher despised by his awful, sullen, computer-porn-addicted son (Daryl Sabara). Without revealing too much, let's just say that a flowery suicide note turns the kid into a figure of worship — and the movie into a toxic satire of celebrity, hypocrisy, and the power of idiotic suggestion. Williams hasn't been this sympathetic in years