Oldie but a goodie: Dihydrogen Monoxide

One of those jokes that never gets old no matter how many times it's told. Dihydrogen Monoxide. It's responsible for many, many evils. In vapor form it is a major contributor to global warming. It is deadly if inhaled or if digested in sufficient quantities. It's a prime ingredient in hundreds of toxic chemicals, acid rain, and practically every pesticide used globally. It's directly responsible for over 3500 deaths annually in America. Sadly, this chemical is present everywhere from your shampoo to baby food.

(In case you didn't catch the joke. "Di-" means two. "Mono-" means one. So, Dihydrogen Monoxide = H2O, AKA Water)

This time the joker was the Commitee for a Constructive Tomorrow, or CFACT. The jokee was the UN. CFACT passed about a petition asking these dignitaries to endorse the banning of this dangerous chemical. Now, of course there's no telling how many people signed it for fun, or how many refused to sign it. Still, nothing like a good chemistry joke on the unwitting.