Josh Greenfield tweeted that the bug with the Cat Form Druid quest should now be resolved.
The Cat Form quest chain for Druids, made up of three quests, was bugged. That created a large bottleneck for players trying to unlock the iconic Cat Form, as many could not progress past the quest. According to Greenfield, this has now been fixed.
If you were stuck at this step, you should be able to try the quest chain again.
Original report: Wowhead