The Burrow Spiderling battle pet is an invisible pet that is non target-able. That is both fascinating, and frustrating. I love the idea, however, you are unable to target it to upgrade it or Battle Stone level it. Could there be a (lets say) 10 second timer on it when it is summoned from your Pet Journal? Then it can return to its usual state after. I would appreciate it for sure!
Yes, I know I can go battle in Stonetalon for a “green” or “blue” Burrow Spiderling. However! the concept could be used for other Battle Pets, Toys, Quests, etc. I happen to see this happening on the Spiderling ATM.