I found this strategy on Wowhead, but noting workflow mostly for myself.
1) Low level pet, can even be level 1
2) Emperor Crab (P/P) or something with Whirlpool, Surge, and Healing Wave.
3) Nexus Whelpling, Frost Breath, Mana Surge, Arcane Storm.
Things of note. Surge will always before Mr. Terrible moves. Healing wave will not.
Step one: Carry pet comes in. Gets hit, swap out. Bring in second crab pet.
Ask the questions per round:
Does he have Spiked Skin?
repeat until he does Spiked Skin.
Does he have spiked skin, but you have more than 70 health?
Does Mr. Terrible have less than 800 health?
If he doesn’t have Spiked Skin, Surge, then Healing Wave.
If he does have Spiked Skin, pass, then Healing Wave.
Whirlpool hits, Surge once more as required.
If he’s STILL alive at that point, Whirlpool again, and repeat last whirlpool pattern.
(Try to end this fight with at least 500 health)
Carroteye comes out.
Healing Wave if it’s up, otherwise Surge until dead. With luck the carrot will be almost dead.
If the Carrot isn’t less than 1k health before the crab dies, forfeit.
Bring out Nexus Whelp, Frost Breath if Carrot is under 500 health, otherwise Arcane Storm and Mana Surge.
Sloppus comes out. Either continue 2 more mana surges from prior round, or Arcane Storm, and Mana Surge. Frost breath to end it if needed.
And after all that, even THEN sometimes it fails. Pet battles can make me so mad. A crit, or a string of misses on the last pet and you’re done.