The Merge Dragons Cat Dragon was available as rewards during the Paws And Claws Event November 2018. (Video below)
There had also been a Pets event during the summer of 2018 but I hadn’t started playing the game yet.
You can presently purchase Cat Dragon Eggs in the Dragon Egg Store with Gems.
I merged my Pet Special Rewards level 1 to level 2 and when tapped I once received a Cat Dragon Egg!!!
The Tier 2 Cat Dragon is the Kitty Dragon, can’t wait to discover it!!!