Myrtle, Myrtle the Turtle (her chip is registered as 'Myrtle the teenage mutant ninja turtle'), Meshcrob, Mee-crob, Scrootles, Scrootle-doot, Mee-scroot, Burcles, Burclur, and occasionally 'dog'.

Maggie, aka Maggie Moo, or Moo, Mooster, Moo-Diggity and several other variations. The ultimate form is Moodelayheehoo

Freddie, Fred, Ferd, Frodo, Froodlehopher

Banjo, aka Beebs, Beebie Jeebie, Beanie Jeanie, and ultimately Bibbertyjibbert

Todd, Toddster, Tupelo, T-Dangles, and Toodleoo.

Juniper, Juney, June bug, Joonie boonie, June Buggie. (Ultimate form unknown. She’s new.)

Aaargh the desire to talk about my cats vs the reluctance to share PII

How about a friend's pet? I call her Babs, Babster, Bibbity bobbity-bette, Bah-bah and Boop

Then there's Daphne, or Daph, Daffodil, Daphodile, dill pickle

Scrappy is Scrappy Doo, Scraps, Scribbles, Scrape, and Shitbird/Pissbird, depending on which one he's doing on the stairs

My current cats are Tiabeanie and Rayla.

Tiabeanie is known as bean, bean sprout, sprout town, bean town, beanie baby, beanie butt, baby butt, sproutsalot, lil booger bean, tiny butt, and lady meows.

Rayla is known as Ray-bay (used to be “Ray-be” like baby, but it sounds like rabies), Rayla banana, banana, bananajam, stinky butt, and various other things when she’s annoying which is an absolute ton. I wouldn’t say banana is in any way related to Rayla name-wise, I started using it as a joke “because banana rhymes with Rayla!” (It doesn’t at all, for you ESL folks)

For Siegfrieda I guess the foundation is her own name?

(Not in the pic: Schweinekatze, Arschkopf, Escandalosa. Sorry for not translating some/all, but it's a bloody mess.)

For Kika it's any word with /ʃ/ or /ʒ/ lying around. We called her "gata chata" (annoying cat) so much she started associating the sound with "humans want to give me petting/attention/food".

This is Roogie, short for Arugula. Roogie becomes Roog Boog. Or Roogie Boogie. Or Roogbert.

Or if he's feeling spicy he's Roogiberto.

*edited formating.

Daisy (real name)

Daisykins

Daisy-waisy

Daizer

Diesel

Doof, Doofy, or Doofus

Dingus

Deezer

I'm looking for a good chance to get her with a "deez nuts".

Lucille Lucy Luce goose Itty bitty luce goose Itty bitty luce goose with the tiny caboose. Luce goose in the hoose (house)

Doobie (real name)

Doober

Boober

Bubber

Bub

Doobus Goobus

Doobius Maximus

Doober Boober Super Pooper

Asshole

Food (you say the f word around her and it gets her attention immediately)

Peanut Butter Cup (real name)

Peanut (common name)

Peeeenuuuuut

Spinach (inspired by a comedy sketch that pronounced it like peanut)

Pee is stored in the nut

Fucker (unrelated to her real name)

molena is her name. shmolena shmlail shmlain baine shmolena baina and then i normally call her a good girl

My beagle girls name is Fancy Pants. Her full name is Princesss Fancy Pants "Silly Bonks" of House Cuddlepup and her many nicknames include fancy girl, fancy beagle, fancy lady, fancy princess, fancy removed, cuddle pants, snuggle pants, zoomy pants, grumpy pants, sleepy pants, wiggle pants, doofus, dingus, stinky, stinky dingus, and cutie snoot. My boss calls her "the beeg."

my frenchie: freddie boy, freddie spaghetti, frederick beauregard (when he's naughty), my baby boy, little mans, little baby mans, stinky boy, stinky little mans, poopyhead. lol

My wife’s cat:
Hazel (real name).
Fluffy (root nickname).
Floofers.
Floufy.
Floof.
Fluff.
Fuckin’ cat.

I have a note file on my phone with names I've caught myself calling my cat by more than once, it's currently 26 lines long.

My cat's name is Sky, absolutely nobody calls him Sky, he is kitty cat

Not in my case.

The cat: Splotchy
The nicknames: Terrorist, Mr Right-in-the-way, What Are You Doing, and Kee-ton

The cat: Domino
The nicknames: Goth girl, Princess, Sweet-pea, Miss Fluffy Pants

Sometimes pet nicknames start from their government name, but her nickname of Muppet is based on her being a Muppet and not her legal name at all!