During the Battle for the Center of the Earth, Dalaran crashed, and a large number of NPC characters disappeared, and in the latest data mining, six large versions of the dog that accompanied the player survived and became the player's pet.
The dog's first appearance was in the Pandaren Mystery version, where it appeared on the farms in the Valley of the Four Winds, and the dog NPC reacted uniquely when the player used the /pet or /love emotes.
In the King of Draenor version, the dog NPC was moved to a stronghold, where the player can interact with it.
In the Second Arrival version of the Legion, the dog was kept in Dalaran Breney's pet shop, and this was the case for several subsequent versions.
It wasn't until the crash of Dalaran in version 11.0 that the designers once again thought of the dog, which survived the crash and became a combat pet and was no longer separated from the player.