The word "squirrel" is one of those inherently funny words, like "chainsaw" or "bazooka".
One of the most memorable "Dilbert" comic strips involves Dilbert writing a computer program to predict the course of the rest of his life, and the outcome is a prediction that he will be kidnapped by "the evil squirrels" and forced to work in their "nut mines".
I think squirrels are really cute and cheerful animals. We have several living around here, and they come every day for sunflower seeds. Sometimes when I go outside one will sit in a tree, shake his tail at me, and make "cussing" sounds. Usually I make similar sounds right back at him.
The story I linked to is funny for two reasons: it involves a squirrel going absolutely bonkers (hence, "squirrel frenzy") and because this enraged squirrel was dispatched with, among all things, a crutch wielded by a 72-year-old man.
Despite their cuteness they have teeth and claws which are certainly no joke. An enraged squirrel is clearly a force to be reckoned with.
I played a computer RPG, a sample game included with Electronic Arts' Adventure Construction Set, in which you played a guy in the ancient Middle East. Every time you crossed a river you risked running afoul of an "enraged hippo". For much of the game your best weapon was a sling; the story of "David and Goliath" notwithstanding, a sling doesn't do a hell of a lot of damage, particularly not to an enraged hippopotamus. And so now the phrase "engraged squirrel" is giving me a smile.
...which gets me to wondering what the DC (difficulty class) is for an enraged squirrel? In Advanced Dungeons and Dragons an ordinary house cat could do one hit point of damage per attack; that would kill most 0-level characters--but I don't know what the statistics are for D&D Third Edition.
And of course you could also have a dire squirrel, which would probably do 1d6 per attack and get three attacks per round...but now I'm just geeking out. Oh well.