The Kooky Zoo Series is a great one!
There's just something about these dispensers. They are probably one of the most popular series among diehard collectors. They are classic 70's Pez!

Cow "A"
This is the first of the Cow series. He is called Cow "A" and comes in many pretty colors. The thing about him is his eyes. The eyes are a separate plastic piece, as is the nose, but the eyes are also found on other Kooky Zoo dispensers as well. Here's a close-up...

Can you see the whites of his eyes?
Another thing to look for is the cheeks.

The Cow on the right (Made in Hong Kong) is called a Partial Cheek. See how a portion of the cheek is missing? The one on the left is the normal (Made in Austria) Cow A. This Variation can be found on other Kooky Zoo dispensers, too.
Yellow and orange...

Look at all the beautiful shades of yellow. There is another that has eluded me. That's a neon yellow. That is on my Christmas list. But wait, there's more!
Blues

Here are some shades of blue. The one on the right is the powder blue. Due to my cheap camera, it's not easy to see, but the powder blue has just a hint of violet to it. Almost an iridescence (had to find the spell check to use that word).
Let me try another shot at the powder blue on a black background.

That's a little better. I still want a new camera.
And another HTF (hard to find)...
This is the green Cow A.
And Purple...

This guy is pretty. Like the green above, he's on a 3.8 USA stem. These were "Pez Experimental Era" dispensers!
Cow "B"
This one probably comes in more colors than Cow A, at least the combinations. Here's a few...

This guy's cousin is a dog. See, the head of Cow A, with a touch of modification, can become Yappy Dog. Let me explain.
Can you see the similarities?

Remove the horns, nose and ears. Slap on a set of floppy ears and a new nose, and walla, you have Yappy. You may also notice that the pusher/kicker on the Cow has a small nub on it, and that the Cow has two holes on each side (one is just barely visible by his ear and the other is where the ear goes). Well, from what I've seen, Yappy can have the nub or not, and he can have two holes or just one. The Cow can have the nub or not, but I've only seen him with two holes. That was a lot about nothing, huh?.
As long as we're talking about Yappy, let's keep that thread going.

Here's Yappy Dog. He's usually found on the 3.4 Austria stem and has a cool IMC (Injection Molding Code). Most dispensers have a single digit IMC located on the upper part of the stem, but some of the 3.4 (Patent 3,410,455) stems will have an IMC that begins with a 4 and is followed with a smaller (in size, not numerically speaking) single digit. Here's an example of a "4 2" IMC found on the yellow and green Yappy above.
I like these Dual IMC's!

Interesting to note. The IMC can go from a 4/1 to a 4/8. The reason is this. The molding machine had eight cavities and each one was numbered 1-8. The large four denotes Austria.
Raven
There are a couple Variations with this guy.

One that's not pictured (he's on my wish list too) is the Raven with Long Beak. The above are the Short Beak variety. The one WF (With Feet) has the dark blue head. You might be wondering, Rob, the two yellow beaks appear to be the same. No siree, Rob. The two Yellow Beak, NF (No Feet) look similar, but have a looksee below.
Cool springs!

The one on the left is what I call the Hong Kong Metal Spring. The right is the more common Austria Metal Spring. These HK Springs are common on the Partial Cheek dispensers mentioned above, but not very common as far as Metal Springs are concerned. And here's the different stem markings of those two Ravens.
Made in...

Left is Made in Hong Kong...Right is Made in Austria
And remember the Cow A cheeks?

Raven has the partial cheeks, too! See the hinge hole on the partial cheek?
Cat with Derby aka "PUZZY"

And yet another Partial Cheek. The black head (far left) is the normal Austria 2.6. On the far right is the normal red head, 2.6 Austria, but the red is more intense then the middle two. The ones in the middle are both partial cheeks. One is a 3.4 (metal spring) and the other is a 3.9 (plastic spring). Both are made in? Right, Hong Kong. Variations seem to be endless :)
And, with Hong Kong, you get...

Cheeks and...

Hong Kong Springs!
Made in USA!

Here's another cool Puzzy. The yellow head guy is quite uncommon. See how Puzzy has the same plastic eye piece as the Cow A?
Cockatoo

Another dispenser known for it's many different colors. It's common for the stems on these guys to have no patent number marked on them. And be sure to look for the "Eric Pyramid" nub on the back/side of the head.
Panther

I hate to admit it, but I can't find a Variation with this guy. The one above is on a 3.4 Austria stem. Still, I think he's gorgeous!
Here's my first! Croc!

Here's my very first dispenser, Croc (2.6 pictured center). A gift from my girlfriend (and now wife), in 1976. She stuck this dispenser on my birthday cake. It's still rusty inside from the frosting. I've been collecting them ever since. Boy, is she ever bummed she got me started :) The one on the right is a 3.4 Austria and the one on the right is also a 3.4, but with feet! This was a gift from my non-genetic son on my 40th birthday! I'm surrounded by nice people bearing Crocs!
And here's Panda.

The above are the older "Removable Face Pieces" version. They also have a little tuft of hair on their heads.
Want a close-up?

Ask and ye shall receive.
Then there's Panda B...

Not much to this guy. But wait, there must be some Variation. There is the country of origin, Czech Republic, Czechoslovakia and Austria. That's pretty good. They can also be found on a 3.9 stem vs. a 4.9. Oh, I got it. How about the ears?
Look at this!

The one on the right is the early release. The fatter ears were added in 1999. Phew! I'm glad there was something different.
And here's the latest Panda!

Cool, huh!?!
And the new Kooky Zoo!

Shown from left are the Elephant, Hippo, Lion and Croc B.
But wait...

Aren't the Crystals awesome? They look good enough to eat.
And look at these new Crystals!

How many more will they make? Hopefully none :)
But they did!

The Zinnafant, I believe, is a promotional dispenser for a supermarket chain in Europe. Don't quote me on that, though. The other is...uhhh...pink elephant. I hate it when I see pink elephants.