I didn't think there was anyone left who hadn't heard this joke already. It's the one about the dangers of dihydrogen monoxide, a chemical found in many toxic substances and often used as an industrial solvent. Sounds scary, but dihydrogen monoxide is, of course, simply the scientific name for water, or H2O. Apparently the city council of Aliso Viejo, California hadn't heard the joke before, because they were about to ban the use of styrofoam cups because dihydrogen monoxide was used in their production. Luckily someone clued them in before they embarrassed themselves even more. Their one comfort is that they're not the only ones to fall for this joke. Last year disc jockeys in Olathe, Kansas warned listeners on April 1 not to drink water because it contained dihydrogen monoxide. Over 150 terrified people then phoned up the city's water superintendent to ask about this dangerous substance, prompting the superintendent to describe the radio station's prank as a terrorist act.