I often wonder about phrase origins. I figured that I would look at the saying "as mad as a March hare" today in honor of both the Easter bunny's visit today and the fact that Easter has fallen in March this year, something that doesn't happen very often.
Rabbits and hares are infamous for multiplying, and I'm not referring to their math skills. As March is the beginning of the mating season that lasts several months for these critters, they tend to be highly excitable and sometimes downright violent. This phrase has been in use since at least the 16th century and was used frequently enough in speech that it was included in John Heywood's collection of proverbs in 1546.
Lewis Carroll personified this famous British simile with his character of the March Hare in Alice's Adventures in Wonderland. Walt Disney's adaptation of Carroll's book into an animated movie depicted the March Hare as a lovably insane creature who was too confused and absent minded to actually give poor Alice the cup of tea that he was trying to offer her. The word harebrained is also derived from this concept and has been in use almost as long as the original phrase.
Hopefully the Easter Bunny that visited your house overnight was a little better composed than most rabbits would be this time of year and has left behind tons of chocolate for you to feast on. Happy Easter!