And since I thought I was going crazy and/or merely lagging, I tried a pet biscuit on both of them. To my surprise both of them grew bigger.
I have no idea how I managed this; I was just playing with my random pet summoning macro while the raid waited for a second tank to queue in. I didn't even notice I already had one pet out until a few summons after the first one decided to stick around. Needless to say, I very much enjoyed having two of my companions following me. :)
Next is just a silly screenshot that I couldn't resist taking. :P
I must admit that I've been a bad pet collector and haven't noticed all the neat details of all the newest pets. There's just not enough time in the day to sit down and simply admire each one.
Anyway, in the same LFR where I had two pets out, I noticed that my character suddenly turned a brownish-green color for a brief moment. I didn't know what to make of it at first, but then I saw I had my Filthling out. Taking a wild guess, I looked it up on Wowhead and what do you know?
The Filthling has an idle interaction and will occasionally spew its guts onto you, applying the Filthy buff (yes, it's a buff not a debuff strangely) which turns you into this gross color. LOL! It even makes this violently ill sound when it does it. How thoroughly amusing. XD