I would have found this even funnier in high school, when I was studying chemistry. Vanity Plate Spells Out Methamphetamine:
Most drivers may be puzzled by the vanity license plate C9H13N, but plenty of crooks likely nod their heads knowingly.It’s the chemical compound for methamphetamine, and despite a state law that prohibits references to alcohol or illegal substances on vanity plates, it may be perfectly legal.
Bradley A. Benfield, a spokesman for the state Licensing Department, said such a license has been granted to the owner of a black 2002 Audi registered in Seattle. The plate may be legal because the same compound represents amphetamine, a legal substance when used in medicine.