From feedback:

The Scratch add-on includes a cat block, so I'd love it if you could remake it so that blocks like Gobo, Terra, and Giga could be added. I'm sure other users would enjoy it too. I know it's a lot of work, but I'd love it if you could create other "add-ons that add character blocks." I'm looking forward to it!

We probably shouldn't use the Scratch mascots for this because they're trademarks, but I think the idea itself is good since cat blocks are now a vanilla feature for members.