What white elephant is, and why it works
White elephant is a gift swap built around one tension: do you open something unknown, or take something someone else has already shown the room? Everyone brings one wrapped gift, players take turns in a drawn order, and each turn is a choice between unwrapping a new gift and stealing one that has already been opened. That tiny decision is the entire game, and it produces most of the laughter.
It is popular at offices because it needs no knowledge of anyone's tastes, and it scales from six people to a few dozen. The main thing that can go wrong is unclear rules, so the best preparation is a single printed page that settles the steal limit and the end of game procedure before anyone picks a gift.