The rabbit, and the egg are symbolic of rebirth and fertility and are tentatively linked into Christianity, pasrticularly the Easter myth.
In reality Oestre (the Pictish/Celtic goddess) was the fertility goddess, and was celebrated in spring time (usually around Beltane, 1st May/Mayday) as she cast the gloomy cloak of winter off of the land and the plants sprung forth in spring :)
Oestroegen anyone? The female hormone?
I actually believe that in this instance, it was The Underpants Gnomes...