When gazing upon an automobile's smooth, unadulterated surface, some people are overwhelmed by the desire to glue shit to it. Eventually these people find themselves the proud owners of an art car, one of those urban contraptions that make people wonder who's in it as much as what's on it. Some purveyors take the strength-in-numbers approach, amassing single items and championing quantity, and there have been fine things happening with buttons, corks, spoons, circuit boards, Pez dispensers, pennies, trophies, televisions, and cameras. Others appear unable to pass a pawn shop without popping in for a little something for the hood. Many dispense with Detroit design, turning their vehicles into great rolling bananas, shoes, sharks, or animals. One of the best things we've ever seen is Oakland resident Rebecca Caldwell's Carthedral, which has a gothic church atop a hearse, with a barely visible VW Bug tucked in there like a corpse. (She also has an excellent riposte to the "Why did you make it?" question. "Someone had to," she says on her Web site.) Obviously, these kinds of people love to show off their plumage, and they get many opportunities at this weekend's Art Car Fest. It starts this morning with the daylong Amoeba to Amoeba Caravan, followed by the Sunset Gala in Berkeley and a pit stop in Santa Cruz. On Sunday it lands in its spiritual home: The How Berkeley Can You Be? parade.