Young Bill Peet is an animal collector and his room is full of frogs, spiders, toads and harmless snakes. One spring he decides he would like to add to his collection with a large boa snake. His parents and younger brother are not in agreement with this, so Bill chooses a capybara, a large rodent that looks a lot like a guinea pig. At first no one in the family is to sure about their new pet. But it takes no time at all for everyone to fall in love with Capyboppy, a name Bill's mother gave the capybara. Capyboppy gets to play in the backyard and swim in the pool and even lay on mother's lap while sitting with the family in the evening. Until one day Capy starts making a "mud wallow" in the backyard and the family soon realizes Capy doesn't fit on the couch with mother like he use to. What will the Peet family do and what will happen to Capy?! 62 pgs.