I have a particular fondness for vanity pets in MMORPGs. Sure, I know they’re silly fluff, but they’re an added bit of personal customization and expression, plus I enjoy how they trot faithfully along with me no matter what fire-blasted hellscape I visit. So I wanted to share my favorite pets in each MMO I play, starting with World of Warcraft!
1. Egbert
Egbert is a total doof. He can’t ever hatch out of his shell, so he’s running around like a madman, er, madbird with it still on. He’s ugly in a cute way with those bulging eyes, and every so often he gets hung up on a particular place while you go ahead, and then he all-out sprints to catch back up with you. At least I think that’s a feature instead of a bug!
2. Willy
Willy and Egbert seem to go together (I think they’re both Children’s Week pets, but I can’t be bothered to look it up right now). He’s a dorky beholder-like thing, with tiny tentacles, an oversized front tooth, and a bewildered expression. I’m not usually one to use flying pets (I don’t like the camera interference), but I like how Willy once in a while will zap a critter. He’s pretty awesome that way.
3. Macabre Marionette
I enjoy pets that actually do things and have fun animations, and this one is all about that. This skeleton continually rocks out as if he was at a metal concert (I think it’s also the Forsaken male dance emote). He’s fun for dungeon runs when I need a team cheerleader urging us on.
4. Perky Pug
I grew up with a pug and had another one as a young adult, so I’m really fond of these stupid dogs. This one gets all the pugisms just right, including the wagging curly tail and scooting his butt across the carpet.
5. Netherspawn, Son of Netherspawn
First of all, best name ever. Doesn’t make much sense unless it’s talking about slimes reproducing asexually, but still, great name. Second, I always wanted a slime pet back when they were extremely hard to get due to a low drop rate (I tried grinding for them but gave up). Third, the squealchy sounds it makes as it moves is both creepy and delightful.
6. Sinister Squashling
It’s an ambulatory Jack-O-Lantern! I have always adored this pet, with it’s wild animations, its unique look, and the fact that it occasionally “disguises” itself as a regular Jack-O-Lantern. It’s one of my most-used while adventuring, so you’ll probably see me with it more than the other pets.
Bio Break 
Great list, but definitely missing Feline Familiar. I just adore that kitty with it’s wizard hat and very own broom when you mount up.
One amusing bug with Egbert (that has been fixed) was that when he ran around he could trigger events. I remember at Arcatraz gauntlet that caught all of us off guard back in Burning Crusade because Egbert decided to zip down the hallway to the last boss.