My gf totally blindsided me with this. I never knew she wanted one. The owner had this cat for seven years, kept fairly good care of it (although we’ll need to wash some dried mud off). I thought seven was kind of old, but my gf disagreed.
For now we’re keeping it in the garage, introducing the dogs, and learning about its care.
Pictures forthcoming.
Them’s good eatin’. 
Congrats! Pets are good.
Picture time. Kizzy and the new cat.
So, an employee found two stray kittens she’s been caring for. She asked us if we’d take one, we declined. She’s asked/cajoled repeatedly, but it just isn’t what we want.
This morning I messaged her that we got a cat. She was pissed! I got four texts in a row telling me how rotten we are. I sent her the picture and now she’s quiet. AITA?
Got me.
Have you looked underneath to see if it needs to be fixed?
I know cats are natural chameleons but WTH is the beastie in this pic?
ETA: SHIT! I BEEN WHOOSHED BIG TIME!!
You won’t be laughing when it jumps on your kitchen countertop.
Not. Amused. 
I wanted feline, kittycat pictures.
… or sits on your laptop.
You’re not the asshole, but I don’t think she is either, really, though she does owe you an apology for texting before thinking (IMHO briefly being a jerk isn’t the same as being an asshole, but YMMV). You’re not an asshole because taking on a kitten is entirely different than taking on a middle-aged cat - and your new cat isn’t old as your girlfriend said, because it’s probably within a year or two of the midpoint of its life - and it’s also natural for the coworker’s first reaction to be WTH? before she thinks through the fact that it’s totally different - she should’ve put the phone down before being a jerk, though.
Kittens need a ton more supervision and ideally if you’d taken on one of those kittens you’d of taken both because babies do best with a buddy to distract them from being lonely and/or destroying your house. The most difficult part of raising Linden and Poe last year were the first three weeks: the two weeks before Poe was well enough to bring home were brutal because Linden was so unhappy being apart from his mom and litter, then the first week of adjusting to two kittens was less difficult than that but more difficult than any time since.
Some adult cats are happy to be an only cat, and others aren’t. Even if you decide to get the cat a sibling, you might get another middle-aged adult, who also isn’t going to be super needy and need close supervision.
Hopefully coworker’s silence now is reconsidering just these things, because it probably has occurred to her that generously taking in a cat who needs a new home has little to do with your liking kittens or not.
So the joke is that you deliberately didn’t capitalize Cat like it should be as a brand name and you’re laughing at people who didn’t get your “joke” and were “fooled” by the way you deceived them?
Do I have that right?
The joke on here is fine. I think the AITA question is whether making the same joke to the person who had been trying to find a home for a kitten was a bit mean - especially with a long time delay on delivering the “punchline”. I think a text immediately follow by the photo would have been fine. The delay on the reveal was maybe a bad idea. But hard to judge without knowing the personality and sense of humor of those concerned.
ETA: rereading what you wrote, maybe you weren’t intending a delay, and she just bombarded you with 4 texts before you could deliver the punchline. In which case, not really your fault.
At least “Arctic” is spelled correctly. Hell, it could have been ArtiCat. Adorable, no? 
Take another look at the “cat” he’s pulling her leg and ours. Took me a few confused minutes to get it and unwind my recreational outrage over snubbing two kittens.
Such a funny guy 
snerk
But looks aren’t everything. 
If you knew the woman, you’d understand. She repeatedly gets in over her head with kittens she finds or takes to find homes for. She knows we do not want a cat, but sends pictures along with begging, saying the cats need homes or else.
She’s laughing now. My “joke” was pushback that she deserved, and she’s sharing it with her friends.