Most Christian Holidays have a pagan equivalent. The pagan rituals were just rolled up into the Christian ones. (One of the early chapters of The Da Vinci Code discusses how the Catholic church spent a lot of time trying to turn pagan symbology into Catholic symbology.) Anyway, I'm sure the history of the Easter Bunny is pagan in origin. Check WikiPedia for a full discussion.
[The original Easter Bunny myth comes from a pagan holiday which was celebrated on the Vernal Equinox. According to Pagan legend, Ostara, the goddess of spring, turned a bird into a rabbit. The rabbit was supposedly able to fly as fast as the bird could fly, but it was still disappointed that it was a rabbit and not a bird. Ostara had pity on the creature, and one day out of every year, on the Vernal Equinox, she allowed the rabbit to lay eggs like a bird. Due to the proximity of Easter and the Vernal Equinox, converted pagans continued to associate the myth with their new holiday, and the idea has been passed down ever since.]