The Hat Mouse is a minor character that appears almost exclusively as a vendor for selling cosmetic hats to the player. Since they are in fact a mouse, a high/squeaky voice would be ideal. Note: Hat Mouse' lines being misspelled could just be bad spelling (as they are a mouse and it'd be difficult) however, this misspelling characteristic persists into normal dialogue as well. Ultimately, ignore any strange spellings of words and opt to focus on the voice itself.