This is The Bumble. I got him from a Menagerist Goblin sometime after Season 10 ended and before Season 11 started. The flavor text for this pet says: He likes the snow, but he’ll follow wherever you go.
Here is the loot dropped by the Menagerist Goblin after I killed him. It’s super obvious that The Bumble was a Legendary item. I had never heard of it before, but concluded that it must have been a pet.
The Bumble item went into my bag. The flavor text says: This little thing may grow up to be huge. Players have to click on the pet item in order to unlock the pet. The pet automatically gets moved to your Wardrobe, with the rest of your pets.
As you can see, The Bumble is a rather large pet. It picks up gold for you.
Here’s The Bumble standing next to Everard the Crusader, for size comparison.