A for Albatross:
   "An Albatross around one's neck" is usually used by those who never read the opium-addicted Romantic's poem, and -- more importantly -- who don't have the foggiest what an "albatross" is.

B for Birds [and Bees]:
   If you were really taught about "the birds and the bees," you are NOT prepared to have sex.

C for Cat:
   A "cat nap" is a short sleep. I had a cat. It slept eighteen-hours a day, usually for several hours at a time. [Also, "'til the cows come home" means when you put the feed out. They will reliably show up. If your cows are coming home late, that's on you.]

D for Duck:
   Re: "having your ducks in a row." Baby ducks naturally follow in a line. If you're having to man-handle your ducks into rows, you should learn wu wei - the Taoist principle of effortless action. 

E for Elephant:
   If there's "an elephant in the room," it is definitely not a good time to talk matters over. Get the hell out, now!

F for Fish:
   "Fish out of water" may be fine, but -- to be fair -- "man in water" is just as accurate. A little waddling Gentoo Penguin could outswim Michael Phelps in the 400m and be finishing its kipper snacks while Phelps was still slogging through his first length. And Phelps is among the fastest our species can put in water. If the average human were dropped in the ocean, he'd thrash around until he got a lungful of water and died...and that's a kilometer offshore.

G for Goose:
    With respect to a "wild goose chase"... fun fact: if you chase a goose, it might well chase you back. I once read a book on the most dangerous animals (for humans) and, to my surprise, the goose was in it. They don't kill many, but they put their fair share of people in the hospital with beak-cracked shins. 

H for Horse:
    So, about "straight from the horse's mouth." If you got your information from a talking horse and are proud that it was 'right from the source,' you might want to consider cutting your acid blotters into smaller pieces. 

I for Indian:
    Not sure how the term "Indian burn" came to be, but I've lived in India for almost a decade and have never known anyone to induce a friction burn by twisting the forearm of another person. You may be saying, "Well, it's meant as in, 'Native American burn.'" But I still don't see any evidence for that. [Don't get me started on 'Indian giving' as an insult against someone who has the gall to want their stolen shit back.] Now, if you called it the "shitty little American schoolboy burn," that -- I would totally buy. 

J for Jackal:
    Jackals are, like anyone who's ever eaten at McDonald's, opportunistic omnivores, but to make them out to be the exemplars of "exploiting situations' is a bit harsh. For example, did you know a Jackal won't cheat on its spouse, even when an opportunity falls right in its lap. 

K for Kangaroo:
    I don't know who came up with "kangaroo courts" but I don't think we know enough about marsupial jurisprudence to cast aspersions upon the Kangaroo legal system. I think it is -- like many instances on this list -- simply deflecting. 

L for Leopard:
   Why would a leopard even want to change its spots? Certain humans (frequenting the Wal-Mart) go to great lengths to appropriate leopard spots. If they are fashionable for a plus-sized woman's stretch pants, why would the leopard think any differently. 

M for March Hare:
   They say "mad as a March Hare" because March is mating season. I think the saying should be "Horny as a March Hare." Alliteration intact. 

N for Nightingale: 
   I suspect ninety-nine percent of those who use "sings like a nightingale" couldn't pick a nightingale's song out of an audio lineup of bird noises. 

O for Oyster:
   "The world is your oyster" is supposedly a great thing. But when I elaborate by saying, "The world is your slimy raw foodstuff that has a twenty percent chance of making you vomitously ill," it doesn't sound like a good thing. 

P for Pony:
    We need to stop people from bitching about the fact that their pony only knows one trick. It's a fucking pony. You should be grateful it knows the one trick. 

Q for Quail:
   To "quail at ______" means to be timid in the face of some stimulus. I don't think it's particularly fair. If you were considered a delicacy, you'd be a bit skittish, too. 

R for Rat:
    If you "smell a rat," it's definitely dead, and -- ergo -- will not be plotting against you. 

S for Sheep:
    I shouldn't have to point out that a "wolf in sheep's clothing" is completely naked.

T for Turkey:
    A "Turkey voting for Christmas" is said to be acting against its own interests, but since everybody eats turkey for Thanksgiving and many people have ham for Christmas, I'd say the turkey knows exactly what it's doing. Even if it's one of the unlucky Christmas turkeys, it still got another month of living. Hell, there are humans who rack up million-dollar medical bills for the same outcome. 

U for Underdog:
   The first use of the term "Underdog" was in 1859, long before the cartoon from my youth. Is there an "Uber-dog" or an "Overdog?" How did this even enter someone's mind?

V for Viper:
   "A nest of vipers," is another bit of anthropomorphizing. The premise of the idiom is that it's a group of nasty people getting together. Whereas the snakes in a viper's nest are as likely to be as good as any.

W for Weasel:
    When someone uses ambiguous words to obscure their meaning, we say they're using "weasel words." But as far as I can see, weasels have the good sense to keep their mouths shut. (Unlike those secret-betraying horses.)

X for XYZ:
   People say, "for XYZ reasons" when they mean for an extensive list of reasons that no one seems to know.

Y for Yak:
   Somehow, we use "yak" for the act of being relentlessly chatty, and -- once again -- I must say that I've found yaks to be less than gabby. 

Z for Zebra: 
    "A zebra can't change its strips." See: "L for Leopard."