You know the non-combat companion pet Mr. Grubbs? That's 'im on the right there, the tiny one (image courtesy WoWHead.com).
You get him in the Eastern Plaguelands—but it's tricky. It's not a simple drop. However! It's not difficult. On two characters I've gotten him in 20 minutes' work.
Step One: Get lucky
Get the Fiona's Lucky Charm quest. This is critical. When you get that, Fiona casts her Lucky Charm buff on you. Once you have that buff, creatures you kill in Eastern Plaguelands (any of them, so far as I know, but more on that below) have a chance of dropping a Hidden Stash bag.
Inside that bag, there's a chance that it will have a Mr. Grubbs pet you can have for your very own.
This sounds like a very low drop—a low drip within an already low drop. Two low drops equal "never happens" usually in World of Warcraft (just ask me about my efforts to get Mr. Pinchy). The math says it should take a long time. But there's something to be done about that: overwhelm the math with zombies.
Step Two: Raise the dead
Go to Zul'Mashar. You can see it there on the right. The reason for doing this is that when you run over the graves in Zul'Mashar, trolls pop up four or five at a time and that gives you plenty of easy-to-get-to creatures to kill for a good chance of getting Hidden Stash bags.
If you're in the 80s and have an AoE attack of almost any kind then you're good to go.
Step Three: Profit
Actually, Mr. Grubbs is bind on pick up, so you can't sell him—but the reward is having Mr. Grubbs, right? That's why you're here!
Continue killing zombies until the Hidden Stash bag with a Mr. Grubbs in it appears.
Yes. On both Abethany and Abjekt, I spent only 20 minutes looking for Mr. Grubbs. Actually, on Abjekt, I found Mr. Grubbs wholly by accident. Just fell right into her lap, as it were, and it's Abjekt's favorite companion as a result—the first creature to befriend her that wasn't the result of a demonic pact, you see. Coincidentally, Abjekt killed a giant grubb to get Mr. Grubbs.
But Abethany went to Zul'Mashar expressly for the purpose of getting Mr. Grubbs. It only took 20 minutes' worth of searching—not counting flying time up to Eastern Plaguelands and transport therein.