I just read the newly released CECIL THE PET GLACIER. The MC has a strong opinion about having a glacier for a pet! And what about EARTH TO CLUNK (MC doesn't not want an alien penpal from Quazar). Seems like most PBs with strong characters could fall under this category of having/expressing opinions (FANCY NANCY, SKIPPYJON JONES, PINKALICIOUS, OLIVIA, etc.). Is that what you're looking for?