Edwin Bennion gets dunked during a tax-night promotion at Trolley Square, where taxpayers released some frustration while mailing off their returns at a makeshift post office. Dozens of last-minute filers lined up to throw tennis balls, hoping to hit the button that sent Internal Revenue Service agents (or at least people representing agents) plunging into the tank below. "The idea was to put the IRS into hot water," said KLZX promotion director Dave Hurtt. "Since you get soaked by the IRS, you can soak them back." Participants paid a $1 (tax-deductible) donation to the Utah Arthritis Foundation for three chances to drench the "agents."