A fork was the only thing I could find for perspective when I went to my studio to take these pictures. [i use forks to stir my pint sized commercial glazes]. The mice are colored with red iron oxide after they're bisque and put back into the cone 6 glaze kiln to finish. You can see the one on the right has a hole in it that I probably made with the 'other' end of a needle tool. They're so little, I doubt it matters whether they're hollow or not.
If you just roll out a pear shaped lump and bend the pointy end to whatever angle you like, you can go from there to embellish them as much or as little as you want. They require only a few minutes to make while you're taking a break. I've made turtles and ducks, but they take a little longer.
For the poster who wants something to give away with purchases, they might need some kind of mesh bag or something so they don't get lost in the packing paper or bag. A little bag with a drawstring and a tag, "Mouse in a Bag" might make them remember to keep up with them. Give them a name or make up a species or make a story. If you make them bigger than these, maybe your signature stamp or initials or pottery logo could be impressed into the bottom. Loads of fodder for the imagination! If you have any similar ideas to share, please let me know!