One hippo, all alone, calls two hippos on the phone.So begins Sandra Boynton's classic counting story, "Hippos Go Berserk " Exuberant hippopotamus guests show up in ever-increasing numbers, until an all-night party is inevitable.One hippo, all alone, calls two hippos on the phone.So begins Sandra Boynton's classic counting story, "Hippos Go Berserk " Exuberant hippopotamus guests show up in ever-increasing numbers, until an all-night party is inevitable.