You can currently do this on live servers too if you use an addon that shows quality, but it may take some time since you have to actually enter a battle to view each pet's quality.
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Some things to keep in mind:
- Blue indicates rare, green indicates uncommon.If anyone has information on any missing pets that aren't listed, feel free to leave a comment to let me know the quality of that companion. Keep in mind I'm mainly interested in the pets that existed before MoP was released. ;)
- I don't own all the pets on the PTR, and my collection is obviously not recent or up-to-date.
- The qualities of these non-wild pets could change at any time. This is the PTR afterall.
- I'd like to compare the current non-wild pet qualities with the PTR versions to see if any were upgraded/downgraded for 5.1