Multiple pets?

It's not really a bug, you can have up to 3 of the same (non-unique) battle pet. Right now you can have more than 3 in order to crate & sell and such. They're all pets you have gained across your various characters.

Here is the blue post http://us.battle.net/wow/en/forum/topic/6413172080#1

Source: http://www.mmo-champion.com/threads/1190861-Multiple-pets

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