"Mad as a wet hen." I always imagined wet, angry chooks, running around, dodging rain drops. Mad about being all wet.
And then. Then I noticed my own chicas ran out into the rain, and paid no mind at all to getting soaked through, sopping and silly. So, I thought "Mad as a wet hen," makes no sense at all.
a : completely unrestrained by reason and judgment
b : incapable of being explained or accounted for
c: carried away by enthusiasm or desire
d: marked by wild gaiety and merriment
e: marked by intense and often chaotic activity!