What’s the most efficient way to create 100+ 2d monsters with animation?

Is there an easy way to create animations for one 2d character and then from that character create several more with different distinct designs?
I was thinking of creating maybe 10 or so 2d dummies of varying size and maybe some that walk on all fours and some that can fly, etc and then after having all of those dummies animated (run, jump, attack, etc.). And I was hoping from that I could create much more detailed designs using each of the dummies and then the animations would just work. Maybe from there I would add a little bit of detail to the animations to make each character distinct. The issue is I’m not exactly sure how to do this and if it’s possible lol.
What would be the most efficient way to tackle something like this? I’m open to whatever ideas and whatever software (spine, unity, blender, dragon bones) that might be best. The game that I want to make sort of requires this and if I can’t figure out an efficient way to do this then I’ll have to scrap the idea.

Well, at the core of it Unity or any kind of animation doesn’t care what type of mesh you have.
It only cares about the bones, their names and parenting hierarchy. So as long as they share the same bone/joint names and hierarcy it will work.
That being said if they don’t share the exactly the same initial positions, then the whole animation might move weirdly, but they will move the same amount of x,y,z etc.

@lunar836 so yes you can just animate your rig as a template, and then apply your model/sprite to the rig.