I was just thinking, bunnies have nothing to do with easter, do they ?
Hersheys (or some candy mfg.) had an idea of how to sell more chocolate.
Rabbits breed like crazy and have long been associated with fertility. The traditional Spring fertility festivals (usurped (stolen) by the Catholic Church as part of their campaign against local religious traditions like they did with Christmas) used symbols like the egg and the rabbit as part of the traditional celebrations.