This is my new hobby, and I wonder if anyone else does this:
Basically, I angle for mirror matches. When I queue for pet PvP, I make note of the opponent's team. After the match, I copy it as precisely as I can (same pets, same abilities, usually the same breed* but sometimes this isn't possible). At the times I'm queueing, I can generally get the same team again about 50% of the time.
This has led to some of my more fun matches. Obviously I have a little bit of an advantage because I've already seen your team in action once. But I also find myself playing with totally unfamiliar pets a lot of the time.
Of course, occasionally my opponent will catch on. One person decided to 'counter' my strategy by playing pets they thought I wouldn't have -- eventually we were playing Netherwhelp/Quilen Cub/X, and they eventually settled on Frosty for the third, which I don't have. Curses!
* The big exception here is if you play a Valk. In that case, I am going to play BB Valk no matter what.