You're as mad as a March hare!

March is the month of madness - at least for hares according to this popular phrase that has been used in English since 1546. This may be because March is the period when males are fighting for the attention of the females. However, the hare reappeared as a character in Lewis Carroll's "Alice in Wonderland" and in the Disney version we can see just how mad the hare is when Alice arrives at the "unbirthday party".
We often add colour to our descriptions by using comparisons with animals according to their (supposed) characteristics, as follows:
as slow as a snail as sly as a fox as blind as a bat
as noisy as a herd of elephants as busy as a bee as brave as a lion
But the expression to use when you don't understand is - 'That's as clear as mud!'