Did you ever wonder about the origin of Groundhog Day, the celebration coming up on February 2? It's a bit of a crazy holiday, when you think about it. A rodent comes out of the ground, and somebody observes whether or not the creature sees his shadow. Based on that observation, a prediction is made as to whether or not we'll have an early spring.
But that's just the simple story line with which the modern world is familiar. As you may well imagine (even if you're not acquainted with the history behind Groundhog Day), the origins of the ritual are much more complex than that. Historians trace Groundhog Day back to Imbolc, St. Brigid's Day and Candlemas Day. Here are some resources you can consult if you wish to study up on any of those celebrations:
Briefly, Imbolc was a pagan fertility festival, with some weather divination mixed in for good measure (thus all the business about predicting an early spring). Brigid was an Irish saint, but earlier she was a Celtic fertility divinity. Candlemas involved a procession with (you guessed it) candles.