Cat

Got my rare in Arathi as a second to a grey small frog.

1. Logout

2. Roll a blood elf

3. ????

4. Profit!

Found multiple times in Netherstorm he seems to be a secondary to everything. just keep going farming your nether roaches and rays you should get one fairly quickly

Just want to add my agreement and recommendation that you go with the single spawn at the cat lady.  Quick respawn and it took about 7-10 battles to finally get a rare.

Thank you...:)  I took suggestion (below) about 'Crazy Cat Lady' and her one spawning cat.  It worked!  On my server there are nada "Fledgling Nether Rays" to be had in the area, so no "Cat" either (and I thought the elusive Tanaris Sand Kitten was a pain)...lol  Anyway, as stated, there is (1) respawning Cat, about every 90 sec, so no wait time.  He is lvl 1-3.  Mostly greys, then to white, green then blue.  Got RARE on seventh pull. Grt plc 2 lv ur 1's.

Managed to snag two rare Cats back to back as secondary pet while farming the Fledging Nether Rays. Caught mine both around Manaforge Duro.

I found a cat on Sunstrider Island, the BE starting area.  There are a bunch of just-critter cats running around The Sunspire building, and one turns battleable now and then.

Also, camping the Crazy Cat Lady's house in Elwynn can work; there's usually only a single cat marked for battle, but it respawns after a couple of minutes.  I finally got my Rare that way.  Cats often show up as secondary in Arathi, but are mostly Poor.

got mine in elwyn forest, he had 121 life at lvl 1, and was a rare, over by the cottage the cat lady lives in.

I found it quite odd, but funny! Battled against 2 Cats in Netherstorm, both 666 HPs. Which is quite a bit lower than the regular lvl 20s in this area.

Captured one, they don't seem to have anything special about them.

I think it's the cat from hell... kinda literally considering it also survived one of the meteor things from the nether roach!

Got a "blue" Level 20 one in Netherstorm - changes colour - summoned a few times and got all 4 alternate Skins.

Also got as as a seconday when engaging a tiny twister in Arathi highlands. He is a different cat each time you summon it/color changer.

Found mine in Arathi Highlands after engaging a Grasslands Cottontail. :3

The netherstorm one seemes to turn into a siamese even though I capture it as another color. Very annoying.

Found only two.

1. Sunstrider Isle  - Blood Elf Starting area.

2. Silvermoon City - In Bank near AH area.

I see these are listed in only 3 starting areas, but I have found them as secondary pets around level 20 twice. Can't remember where the first one was, but the second was in Netherstorm.

Edit: Found more cats in Netherstorm, as secondaries to the Nether roaches and Nether ray fledgelings. Very common it seems.

Sunstrider Isle is probably the easiest place to find a cat that can be captured. There are multiple spawns there, and they respawn very quickly if you have to clear them out. However, they also very frequently show up as secondary fights in Arathi and Netherstorm (of all places), so if you're not picky about hunting for 'just the right model', you can grab one at those locations.

I found mine at sunstrider isle.

I have found approximately 2 cats that can be battled and caught in Elwynn Forrest. they spawn outside the house of Donni Anthania <Crazy Cat Lady>, one in the front and one in the back. The house is located south of Northshire Abby and west of the road. 

update: I have caught the light grey stripped on the north and south side of the house and the siamese on the east and west. I have only captured the cornish rex on the east side near the cattle. I have not caught the bombay.