Cut an opening of at least 2-inches by 2-inches on the top of the creature. Do this with a Dremel tool (preferred) or, depending on the hardness of the toy, you may be able to do it with a sturdy craft knife.

Depending on the size of the toy, and what parts of the body are hollow, you may want to block off a part so water doesn't get trapped, despite the drainage holes. I used some Dollar Store modeling clay to keep water out of the tails.

Sand the edges.

Empty out the body of any dustings and clean it well.

Give your creature some punch with spray paint!

Pop in your plant, (succulents are best because they don't mind tight spaces,) top it off with fresh soil, give it a little water, and enjoy!