Many pagan traditions have found their way into Christian religious observances. Rabbits are one such symbol.
Rabbits symbolize the fertility of springtime.
The rabbit is also the symbol of the Egyptian moon - and the moon is used to determine the date of Easter each year. The hare is responsible for laying eggs and hiding them. This probably evolved from children hunting for Easter eggs and scaring away rabbits which happened to be in the area. The hare and egg provide a link between the pagan faith's welcoming of spring and Christianity's Easter celebration. The custom of decorating eggs goes back many thousands of years.