Sparky, your response made my day.

I'm so glad you enjoyed the card so much. And wow, you recognized a lot of characters!
As promised, here is my complete guide to the critters and characters who appear on the card:
H: A vaguely Chinese-type dragon with a ridiculously tall nose horn and long chin barbels.
A: This leopard seal sez: “I has a bucket!”

(And yes, it
is a reference to that DA picture of yours.)
P: Ozzy is not happy about being made to wear a party hat.
P: Strut doesn’t mind his hat; he’s just trying not to crack up at the scene in front of him…
Y: Sierra doesn’t like his hat either, but is making the most of the situation by expressing his disdain for a certain former boss of his through mockery.
S: A party amphiptere (pronounced “AMF-ih-tare”), one of my classic card creatures. I may have explained them to you before, but just in case your memory needs refreshing, they’re little serpentine dragons wearing party hats who appear on nearly all of my cards. Sometimes I choose to “ëptere-ify” certain people or characters. You might be able to guess from the colors and the way it is reacting to Sierra who this one is supposed to be.
E: A very fluffy raptor, standing on its head. I first used this character (in this exact same pose) in my oldest younger brother’s own second schnappszahl card earlier this year. I was so happy with the character that I’ve used him in three more cards since then, including this one.
C: Your OC Chimera has hit the jackpot!
O: An ouroboros (not quite sure of the pronunciation: something like “oor-ROB-or-us” or “or-ROH-bor-ROHS”), a symbolic dragon or serpent that holds its tail in its mouth, representing something cyclical or infinite. I thought it seemed appropriate for a birthday card. I was originally going to give it more draconic features, such as horns, spines, and a bladed tail; then I decided to give it a simpler design, and have it be simply a horned snake; ultimately I just gave it a horned helmet.
N: Seven of your favorite villains in my chibi style. There’s Cama Zotz (plus a tiny Goth to fill in some negative space), El Chupacabra (El Chibicabra?

), a xenomorph from
Alien with a party blower (I just couldn’t resist

), Rudy from
Ice Age 3, my attempt at Venom (he looks more like a demonic poison-dart frog

), a falconfly from
The Future Is Wild, Freddy Kreuger (his chibi design was one of the first I came up with, and I’m extremely happy with it

), and Shadow Lugia.
D: Chibi Lord Shen. Turned sideways with his train spread, he makes a perfect D, so he got to be his own letter. (Man, were his feathers a nightmare to draw, though. He actually ended up looking a lot better than I thought he would.)
S: this inquisitive, wormlike burrowing creature has three eyes, a chitinous mustache, several luminous-tipped tentacular appendages on its head and tail, and is probably an alien.
C: Cookie eating a cookie. Yeah, I’m very pleased with how cute she came out.
^.^H: This creature is part llama, part unicorn, and part Truffula tree.

It probably comes from the same world as the Swogglehorn (from that card I showed you before).
N: An assortment of aquatic antagonists, all chibified again. We’ve got Bruce the shark from
Jaws, the LBT IX
Liopleurodon (or your character Lio, if they’re different individuals), your OC Top Notch the orca, a
Future Is Wild lurkfish,
Ice Age 2’s Maelstrom and Cretaceous, and the odd one out: the Pillrus!

(He’ll be fine, by the way; his skin is too thick for Cretaceous’s teeth to penetrate, and he’s too fat to swallow.

)
A: Toni and Stygia forming a “totem pole” along with a small fuzzy mammal (perhaps the one you adopt in the RP?) wearing an oversized party hat.
P: I call this guy a marble dragon, both because of his shape and his color: two contrasting yet complementary shades in a somewhat marble-like pattern. I first designed this character during my camping trip in August, and like the party amphipteres, I am planning to make them a regular fixture in my cards. You get to be the first recipient of a card containing a marble dragon.
;?)P: Spazzy Sparky the ring-tailed lemur, standing on her head! (What can I say? Upside-down animals are funny!)
S: The Lizard. He may look a little surprised to see you, but I think even he’ll agree you’re pretty cool for a mammal.
Z: An assortment of buggies (No need to chibify most of them since they’re already tiny enough to fit). The antlion is probably Apep (If he was Picasso I probably would have given him a little beret and a paintbrush

). The mantis’s appearance is based on your OC Hisoka, but the hat and bindle stick are a reference to the mantis I encountered in Utah this August whom my family named Hobo

(photos in
this thread). The chibi jumping spider is indeed based on Naira (jumpers are
SO. FREAKING. CUTE, and just
made to be chibified). The six-spotted tiger beetle can be either your OC Zoomer or one of your pet beetles, whichever you like. I didn’t know what species your former pet stag beetle Takeo was, so I hedged my bets and based this stag beetle on a combination of the
Dorcus beetles that live in Japan and Akibiki, the
Lucanus mazama stag beetle I met in Arizona last year, so he can default to being the latter if he doesn’t look like Takeo. Above him is Jade, your white-faced hornet OC. And the last bug is a slightly more realistic version of a certain psychotic grasshopper I’m sure you’ll recognize.
A: Rattlesnake Jake came to your party, but I didn’t dare offer him a party hat.
H: Yes, it’s the only bat who’s actually happy to have a run-in with Rattlesnake Jake!

(Good thing for her he left his ammo belts at home.) I was originally going to make her a generic leaf-nosed bat, but in light of
the question I asked you a while ago, I tried to make her look more like a vampire bat.
L and
,: Random chibi critters! Can’t you tell what the first one’s supposed to be? It’s a bugling elk!

Next we have the Visayan warty pig (A.K.A. mohawk piggy) from the
Minnesota Zoo photos I showed you, followed by a bored cow (Dang it, her expression looked so much funnier before I drew those black blotches over her eyes!

). Next there’s a chibi kiwi, and finally your dear departed little ratties!
S: Tiki managed to talk Tero into wearing a party hat for the card…
P: …but that doesn’t mean he has to like it.

(Also note how the color scheme of the hat is reminiscent of something else Tero would love to mangle…

)
A: I had an incredibly hard time deciding what to draw for this letter A. I considered everything from Mothman wearing a party hat to your OC Piercer the skewer, but I couldn’t manage to get any of them to fit an “A” shape in any of my practice sketches. Finally I decided on yet another creature that pops up regularly in the cards I make for my family: an extremely fat, bored-looking frog (probably a relative of the “hoppers” from the original LBT). At first I thought I’d just have him wear an oversized party hat, but felt like that wasn’t enough. So then I came up with a brilliant idea to spice things up: a fat bored frog, with a
muffin on his head, with a party hat on top! But no, that still wasn’t enough. Finally I hit on the answer: a fat bored frog, with a chocolate chip muffin on his head, with a derpy chibi dragon sitting on the muffin, with a party hat on
his head, with a candle on top of the party hat! Plus a tiny party amphiptere thrown in for good measure.
Z: A cluster of chibi Honduran white bats (and considering what most of them are doing, what better letter for them to be spelling out?

)
Z: Even Thud is hypnotized by the cute.
Y: Yes, it is the Squid Who Is Inexplicably Wearing Pants! I’m so proud of this character.
S: A cockatrice, a mythological creature (one of my all-time favorites) that was part rooster, part serpent, and could kill with its glance. Mine is a somewhat cuddlier rendition with a color scheme inspired by the red junglefowl and some domestic roosters.
P: Clubbie, festooned with fruit as usual.
A: I knew from the beginning that I
had to draw a skua on this card, specifically
the “flipper boid” skua, A.K.A. Boss Skua. I decided that since the skuas in
Happy Feet already had those mafia accents you love so much, I figured why not dress the Boss Skua in Godfather attire?

At one point I consulted my sister (who loves the Joisey mobster archetype) on what a well-dressed mob boss should be wearing. One of the things she told me was that he should be wearing a big gold ring; I immediately thought of the yellow ID band on the Boss Skua’s leg and thought, “Perfect.”
R: This night stalker (remember them,
the giant, flightless future bats?) is wearing shades for some reason. It could possibly be interpreted a reference to the fact that his species is blind, but more likely it’s because he knows it makes him look cool.

I also felt like he should be holding something in his “hand” (actually a specially adapted hind foot, as you know), so I gave him a candy bar. I actually portrayed night stalkers in a manner similar to this in the stories I wrote a long time ago: scary-looking nocturnal creatures that were in fact just a bunch of overenthusiastic, chocolate-loving party animals.
K: A generic small pterodactyloid pterosaur. I had a tough time deciding on colors, and I sorta fell back on the same ones I used for your dinosona. I guess this could be a “pterosona” for you if you wanted, though I don’t think it looks spazzy enough.
Y: Teryx, wearing one of those giant foam fingers on his tail. (If you look at it upside-down, you’ll see that he thinks that you’re #1.)
!: Dennis the weasel, one of the earliest characters from my aforementioned old stories, along with a tree star.
Finally, we have Guido and my dinosona from the “In The Land Before Time” RP presenting your dinosona with a chocolate birthday cake. And below that, my avatar, wearing a party hat.
I had many other ideas that I wanted to use in this card: Davy Jones riding rodeo-style astride a breaching Kraken; an extremely annoyed Slasher the deathgleaner tangled in wind chimes; your pet rat Domino grinning sheepishly at another character after accidentally knocking something over and creating a domino effect; a vampire bat in a top hat, monocle, bow tie, and possibly a mustache, holding a teacup of blood; your bearded dragon, Monster, meeting a literal bearded dragon (as in a mythical dragon with a big bushy beard); Klepto the frigatebird in pirate garb; a clutch of fluffy cockatrice chicks; and a frontal view of the alien worm (the critter forming the second ëS’) showcasing its three eyes and “mustache”. Sadly I did not have the time or energy to fill in the empty space at the bottom of the card with these characters. The amount of text meant that this was already the most elaborate card I had ever drawn, and even though I started planning it out in late August (and began drawing it in early September), I failed to partition my time well enough to include the extra pictures.

Perhaps I will draw these characters another time (unless you beat me to it

).