GoodIdea that came from a bunch of delinquent FroshChem students (not necessarily all FreshMen), Spring 1999:
Secretly pick a word that ProfessorBaker will say a lot during today's ChemLecture. When she says the magic word, everyone playing crosses their legs. When she says it again, everyone uncrosses their legs. This can get really amusing once Prof Baker catches on and figures out what the day's word is...