2. Achieving. There are many pet battling achievements in game, and following the natural trail through the Taming [Continent] achievements up to Pandaria, and then on to the Spirit Tamers, Beasts of Fable and the Celestial Tournament was an epic journey for me and for many others. It's well worth doing. The Celestial Tournament is still, IMO, the pinnacle of PvE pet battling. However, WoD and Legion and BfA have added more battling achievements.
World of Warcraft Classic is currently in beta, which means some players are getting a chance to experience a much older version of the MMO ahead of its release. WoW Classic is based on how WoW played in August 2006, back around update 1.12. Back then, things were different. Tauren hitboxes were much larger, sitting could cause certain combat effects to not trigger and completed quests were marked with dots and not question marks. Strange days.