Motosin's Comments

I would suspect it would depend on your class's AOE ability, but the Engineers up at Gavin's Naze (the ones working on the seige vehicles) have a ridiculously fast respawn rate and there are about 20 of them.  A couple hours of that, I got the Black Tabby Cat.  3314 kills.  I know that's a bit of a lucky percentage drop for this, but mowing through these engineers is the way to go for farming this pet.

Like a few people said... I can now draw a detailed topigraphical map of the lake in Northern Feralas from memory after circling it killing noxious whelps.  I seem to have been a bit luckier than most, and got it on kill 609 (rarity count).  I can't imagine the 2000+ some people report having had to kill.  

Since today was the first day of the Faire, and I don't have Moon Moon yet (never even tried), figured I would server hop all day to get him.  Every kill, we had about 15-20 people, and I noticed 1 or 2 Moon Moon's would drop, a couple times none dropped.  I got it on my 9th kill of the day. 

1134 Kills (rarity count) for me to get it.  I found the best place to farm (by far) was the Nethergarde Mines.  A continuous loop of groups of 3 to 9, never waiting for respawns.  Mine was a P/H.