When it comes to describing something as small as a mouse, there are many different ways to convey its size. Synonyms for "mouse-sized" might include diminutive, petite, tiny, miniature, mini, pocket-sized, or small. Each of these words has slightly different connotations, with "diminutive" implying a degree of nuance or delicacy, "petite" indicating a certain elegance, and "miniature" suggesting a sense of intricacy or craftsmanship. "Pocket-sized" and "mini" both have a more casual feel, while "small" is perhaps the simplest and most straightforward option. Whatever word you choose, it's sure to capture the adorably pint-sized nature of your tiny subject.