Why Easter eggs? Why bunnies? Why chocolate? And if so, whom? These are unmistakably questions, but the last one can be dismissed as youthful enthusiasm and probably a grammatical error, unless ``who'' would be wrong instead. But if there's one thing to get straight then we would be in much better shape than we likely are. Among the one things to get straight, then, are the folk etymologies which would suggest that ``Easter egg'' is a corruption of the earlier form ``yeaster egg'', that is, an egg to be at the same time one makes yeast-rich bread-based snack foods. These breads would be particularly concentrated on in the springtime, where they gained their association with Easter. While this theory was particularly popular in the late 1970s when nobody felt like making elaborate sugar-covered bread snacks, it is now known the entire story was the result of a hoax played by humorist H L Mencken, who was having a bit of fun at the expense of President Millard Fillmore. There's no need to feel bad for Fillmore, though, as he had his revenge, in a similar prank spreading the rumor that Mencken's first name was ``Henry'' so successfully that many reference books still list that, instead of ``Horace''.
The tradition of hiding Easter eggs comes to us by way of Renaissance Germany, with an assist by Spain and a rebound against Iceland, which otherwise does not figure in this adventure. The problem began with the age-old problem of planting seed for useful or ``cereal'' crops without having birds fly in and dig up the seeds before plantings could begin. So when, somewhere on the upper Rhine, it was suggested they could head off the problem by planting birds instead, it started to sound like a pretty good idea, and soon folks all over Germany were planting eggs in likely-looking spots, only to discover that this didn't even begin to sort-of work.
So with clear failure established they proceeded to make the ritual more complicated, painting the eggs in the hopes that they would get blue-and-white striped chickens or other such things that would at least make the failure of crops the more exciting, and that didn't work either. They then began to hard-boil the eggs, on the grounds that if the cereal crops couldn't turn up wheat or barley or such they could at least turn up something edible, which is the birth of the tradition of finding a prize inside one's cereal. The eggs would eventually be replaced with plastic, which would in turn eventually be replaced with such creations as Tony the Tiger-themed pedometers. During the Thirty Years War the tradition fled Germany, and who could blame it?
That pretty well takes care of where the eggs came from; the question is how they got associated with rabbits. The answer there comes down to the old chocolate forests which thrive (thrived? throve?) in the vicinity of what is now Fall River, Massachusetts. In this cocoa-rich forest a whole chocolate ecosystem neatly sustained itself, allowing colonists to witness the wonder of life through chocolate leaves, rabbits, coyotes, giraffes, and locomotives. For its protection the early City Fathers decided to disguise the real source of the community's prosperity behind the trappings of a thrivening textile industry. The chocolate rabbits could be most easily domesticated and bred rapidly. Their relatively tame demeanors and eagerness to hop into metal-foil wrappers made them extremely popular as pets before it was noticed that other people seemed to get cream-filled or solid ones, while you personally never found them.
As for getting the bunnies -- by synecdoche all rabbits were associated with the responsibilities of the chocolate ones, and vice-versa -- to be linked up with the eggs, that again is pretty straightforward. Several large department stores in New York City and in Chicago tried combining them to save money on storefront displays during the Great Depression of the 1880s, and again in the Great Depression of the 1930s. However, it was not until World War II and the shortages and rationing of that era that the custom spread to most department stores and from there, over the course of the war, to general public acceptance. By 1946 there was just no separating them again, but everyone was content enough with the blend that they only barely remembered how it used to be, which is how it usually works out.
Trivia: 258 vessels carried ice along the east coast of the United States and 95 carried it overseas in 1847. Source: The Frozen-Water Trade, Gavin Weightman.
Currently Reading: The Unicorn Girl, Michael Kurland. Bah. Snippy characters including the author blip through a couple sketchily constructed universes until they can achieve a technobabble implosion. Still, you have to admire an author bold enough to put his version of the Minkowski transformations in the last chapter. It turns out to be the sequel to The Butterfly Kid, by Chester Anderson, the other character in these books, which was nominated for a Hugo in 1968.