Two black miniature poodles, F and M, Belle and Wesley. Interchangeable nicknames.
Miserable Shit Dogs. Der Zwei Kleinen Schwarzenhunden. Les Petits Chiens Noirs. Fucking Black Bitch (Belle only).
Ah, pet nicknames! Seriously, and I wonder why they don’t come when called.
Pandora, f., cat; short hair, dilute torbie: Pandorable, Panhorrible, Grumpy Bunny, Missy Hissy Pissy, Funny Bunny, Bunny-butt. The “bunny” came because she has fur that’s soft as a rabbit’s.
Sebastian, m., cat: longhair, harlequin: Spiggy, Spiggy-wiggy, Pigs, Mister Pigs, Doodie, Little Dude, Rude-dude-doody. Not the sharpest cat I’ve ever had, and he loves food…mine, yours, the other cats’…
Baxter, m, cat: short hair, brown and grey mackerel tabby: Bax, Baxie, Birdie (it was the name of his favorite toy, now he answers to it), Dirty Birdie, Sir Poops-a-Lot (he’s the cat with IBD), Sweet Boy, Mister Handsome, Sweetie-the-Pie. He smiles if you scratch him and call him “good boy”.
Also, they all freeze if I yell, “DAMMIT!”
Oh, and “Inspector Pancakes.” He solves MYSTERIES!
Gideon, cat, male. Furball, Fluffy Little Twit.
Alice, cat, female. Furball, Fatso, Fluffball, Fluffy Little Monster.
Angel, cat, female. Furball.
Timely thread. About 4 years ago, an old friend and colleague of my husband’s brought a Belgian Mal to us - just out of the blue, he decided that my Tony needed this highly trained police k9. (Not too weird. Tony was a k9 handler, and our Mojo was reaching retirement age. But this was a $3000+ dog, and the gift-giver probably could have used the $$. But he insisted, and was having a mental health crisis at the time, and we privately cleared it with his wife, because the giver really wasn’t competent to make decisions at the time - long story.) All we knew about JO was his name and age and a basic understanding of his training. Turns out that JO is a nickname - stands for “Jack Off.” Two other handlers had tried to partner with him before he came to us. Both returned him to the kennel, citing his sheer cussedness. The second renamed him Jack Off. I swear, that is the sweetest, schmoopiest big puppy on the planet. He’d rather have a good belly scratch than bacon. He loves his people, most especially Littlest Miss - that’s his puppy. But in spite of the fancy name on his pedigree papers, he remains “J.O.” We just learned what the initials stood for a few weeks ago. (Before Mojo’s death, though, I usually referred to the pair as Mojojojo. Because who doesn’t love the Powerpuff Girls?)
Other critter is Pandora, the Pyrenees/St. Bernard mix. AKA Dora, Dumb Dora (Gene Rayburn, anyone?), “You Giant Idiot,” Dora the Explorer. I swear, the last Pyrenees* we had was a genius among dogs, but poor Dora must get her brains from the St. Bernard side of the family. She is very very very sweet. And pretty. But I’ve seen smarter firewood.
My mom’s dog is Elwood (because, when she adopted him, our house already had a Jake.) He alternately known as Ellie Mae, Smelly Mae, and “Shut Up, Dammit.” (Best estimate is that he’s 16-18 years old. Ma brought him home after an in-law found him by the West Virginia Turnpike 13 years ago, and the vet reckoned him to be 3-5 years old at the time. Probably King Charles spaniel and something. He’s an annoying little asshole, right up until he snuggles up and puts his chin on your lap and gives you the puppy dog eyes…
*The genius Pyr was Sebastian. Grumpy Bunny might think I’m a copycat, but my Sebastian and Dora were adult rescues, pre-named. 
Higgs: Higglet
Taz: Taz-burger, Taz-a-rama-ding-dong, Tazzer, Rotten Cat (he has occasional episodes of peeing on furniture)
Ziva: Fluffer-nutter, Baby girl. The pic was taken in 2009 - she’s poofed up a bit since then.
ETA: FCM reminded me that Sebastian also gets called “Flufferbutter”. For his fluffy butt. 
I approve of all of these names! (My Pandora is so-named because she didn’t want to come out of her carrier at first, so after a day, I took the top off of it. When the top came off her box, trouble came into the world. :D)
Especially since I had a wonderful, huge, neutered former tomcat (and obviously male) black cat named Mojo, who was also nicknamed Mojojojo. Sweetest cat in the world.
Abby, female husky/lab mix, 8yo
Abbygator, Abby Blabby, Abbykins, Little Face, Little Girl, Growly Dog, Sleepy Dog, Happy Dog
Charlie–cat: Fatty McLardass, Fatty, Boo, Boo-Bear, Boo-Berry, The Baby
Havoc (cat) - Moink, Concrete Meatloaf
Pixel (cat) - Pixie, Assassin, Pixie Wixie Pixie Poo, Pix-Pix, Stinker
Caelan (cat) - LOB, Little Orange Boy, “Get off me!”
Brindle (cat) - Baby Girl, Little Girl
Furbius Maximus Rex (Lord Nuzzles Furball followed by a Long List of Official Titles)is most commonly called;
Kitty Boy, Furry Child, Vicious Kitty, Fuzzy Butt, Fluffy Butt, Puffy Butt, Jungle Kitty, Kitten Chops, Loving Kitty,
Nothing but guinea pigs here for decades - and they never got called anything interesting.
But when we had cats…
Pete (named after the cat from The Door Into Summer) was Pete-a-puss, Petie-pie, Pete-nik, Pete-loaf, and Hippo-Pete-amus. Probably others as well.
Sebastian got morphed into Sebustian, Buster, Fuzz-Buster, and Fuzz-Buzz.
Jasper (mixed terrier): Jazzie, when he was younger. Now, mostly Idiot (seriously, dumber that two sacks of hammers)My daughter’s dog.
Finn (Looks exactly like a cross between a Chihuahua and a Greyhound, if you can ever imagine such a thing. Sold to us as a Chihuahua/Shih-Tzu - saw the Chihuahua mom):
Finnie, Finnie Boy, Finster, Buddy. My dog.
Max (Yorkie/Shih-Tzu mix): Fatass, Lardbut, Fathead - you get the idea. Also sometimes Septimus Maximus. Also my daughter’s dog.
Honey Rose (Pomeranian): Rosie, Ro-Ro. She’s the alpha. My wife’s dog. She’s the alpha too. 
I don’t have any pets, but my mom does. Her dog Brady mostly doesn’t get nicknames, but it’s a very convenient name to sing to:
“Hello my Brady, hello my puppy, hello my ragtime dog”
“B-B-B-Brady, beautiful Brady, you’re the one that I a-a-a-adore”
“You’re once, twice, three times a Brady”
The cat, meanwhile, is really more of a tenant than a pet. She’s officially “Ms. Mousy”, but sometimes gets called “Mouse-kitty”. She also sometimes gets referred to as “the beastie” or “ambush predator”, the latter from her habit of lurking in places people are likely to pass by to pounce out and demand pettings.
Rocco, our African Grey Parrot. Although his name is Rocco on his hatch-certificate (long form), we call him Buddy, and he loves that name.
When I put him in his cage for bedtime, I say, “goodnight Buddy” and he echoes, “buddy, buddy, buddy, buddy”.
A fun and cheerful thread, thanks!
All doggies:
Jack = Yak, Yacky, Collie Boy
Scout = Snout, Girl Scout, Collie Girl
Caleb = Cable, Cowleb, Eduardo, Brindle Butt
Chase = Chasey, Baby, Lil’ Yellow, Stubs
Ernie - Ernesto, Ernie Bernie, Ernie McBernimus, Fuzzbutt
Harley - Harley D. Hogg, Fat Boy, Pokemon
Lucy - Shadow (she follows me everywhere), Lucy Belle, Lucy Boo
Amie - Aimless
Dipsey - Dipsey Doodle, Dipstick, Pissant
Four of them with my husband -
Delilah, dog: Dee, Dee Dee
Bootsy, cat: Boot, Boot Boot
I’m seeing a pattern here…
Oh good, I love the goofy names my dogs have acquired:
Mr. Peabody, male: Peabz, Pooble, Peeble, Big ol’ red bone floppy-faced big headed skinny puppy honey boo boo dog, New.
Gomez, male: Gomer, Gomie, Gomel, Hula Boy, Moose, Gomez Garcia Gonzalez de la Vega, Lau willi willi boy, Christmas beagle pup, Big, Bubba.
Lily, female and sadly recently deceased: Lulu, Squirrel, Loaf of Bread, Loafie, Little, Baby Lily, Bobo, The Kitchen Beagle, Trundle Butt.
No wonder they don’t obey me. They don’t even know who I’m talking to.