Crazy Cats and the Armory

Assuming anyone reading this also has the WoW Armory app, it's a great way to snoop. Sadly you can't check the pet list of a fellow guild member, but a handful of achievements show progress that people are having with pets making it an easy way to see some of the pets they're missing.

Crazy Cat Lady/Man is one of the easiest to both access, and gather missing pets from. Donni Anthania sells five of the cats available for this pet and she's found in Elwynn Forest. Each is only 40 silver (before discounts) so they're super cheap. Dealer Rashaad sells the Siamese Cat if you can get to Netherstorm, Breanni in Dalaran sells the Calico Cat, and Michelle De Rum in Winterspring sells the Winterspring Cub (though I will say the last two are quite a bit higher in price...50 gold).

If you're shopping for a cat lover, pet collector, or someone who likes a lot of titles, this is a good place to start.