The pets I've gained since coming back to playing Warcraft.
Pet 427 - [Nexus Whelpling] - Caught in Coldarra in Northrend. Went there to collect Colbalt and found several of the Whelplings in the wild. Caught one and moved on.
Pet 428 - [Red Cricket] - For becoming Best Friends with Sho of The Tillers a few days ago. Involved flying around Valley of the Four Winds looking for Piles of Dirt containing Gifts.
Pet 429 - [Eye of the Legion] - Loot Card From the WoW Card Game.
Pet 430 - [Sand Scarab] - Loot Card From WoW Card Game
Pet 431 - [Fluxfire Feline] - Found Outside Gnomeregan. I killed Cochroaches at The Toxic Airfield until one spawned. These pets are known for being Over Powered, but are being nefted in 5.2.
Pet 432 - [Lofty Libram] - Found Around Dalaran Crater. I found it in the wild straight away. Didn't have to do anything special to make it appear.
Pet 433 - Harpy Youngling - Caught in The Dry Hills in Northern Barrens. Had to wait around a while before one spawned.
Pet 434 - Infinite Whelpling - Caught in Tanaris outside the Caverns of Time. There were heaps of them around, so just flew in and caught one.