Didn't Get Credit for Achievement - Pet Battle Challenge: Wailing Caverns

There are two quests offered by Muyani for pet battling in the Wailing Caverns. The first quest is a one-time only account-wide quest, Wailing Critters. This quest rewards an Ultimate Pet Battle Stone and the option to port to the pet dungeon from Manapoof in the Dalaran Menagerie. There is no achievement for completing this quest.

The second quest is Pet Challenge: Wailing Caverns, which is a weekly quest which rewards Damp Pet Supplies. Completing this quest the first time also rewards an achievement, Pet Battle Challenge: Wailing Caverns and the pet Son of Skum.