This is clearly inspired by actual ponies.

And nothing else.

In truth, the 3-type cards were originally intended to be the full animal morphs. Mouse would just be a mouse, pony would just be a pony, and whatever the third is would just be whatever the third is.

What changed my mind was mostly the whole "but how do they hold the cards and throw the dice" issue. There's jokes to be had with that, certainly, but I already did that in the first Goonmanji, and this would be the case three times over. As such, I've gone in a slightly different direction.