GMs definitely need to enforce strict "in character" play, eliminate "across the table" chatter, and by doing so - set the scene for an awesome role-play experience!
Gnomes are famous for their festive springtime celebrations. Farm villages will often dye their hens eggs bright colors; with gnomish magic, the chicks that hatch from the eggs have the very same colors. The chickens eventually lose their hues, but the stronger the magic, the longer the color stays. In a gnomish village, one can easily spot the village shaman by his flock of gaily colored fowl.