It is important to note he has the same spawn chance on any difficulty.

That will help increase how often he’ll show up. There is a silver lining for the moment: treasure goblins spawn twice as often this season. The downside is, he is a very rare spawn, so finding him is difficult. Like every other treasure goblin, just find him, chase him, and beat him down for his loot. He has 19 different pets, and will keep players coming back. Better yet, it’s guaranteed that the pet is not a duplicate. Obtaining a pet from him is easy - it’s a 100% drop for everyone in the party, every time he is encountered. The majority of non-combat pets drop from the Menagerist Goblin. Here’s where you can go to find a probably not-cuddly friend. There are a lot of these pets to obtain, but very few sources for them. And let’s not forget That Which Must not Be Named, which is definitely not a reference to the cow level, because there is no cow level. There’s Grunkk, where they smoothed out the details of details of an Abomination. Galthrak the Unhinged which is a demon that is mostly just a jaw. These pets range from the adorable, like the yeti-themed pet The Bumble, to the grotesque, like - well, like almost every other pet.

Not every class in Diablo 3 can have a pet to fight along side them, but everyone can have a non-combat pet to keep them company.

Diablo 3 dragon pet