In which book would you find 'Pushmi - Pullyu'?

The pushmi-pullyu (pronounced "push-me—pull-you") is a "gazelle-unicorn cross" which has two heads (one of each) at opposite ends of its body. In The Story of Doctor Dolittle, the grateful monkeys in Africa persuade it to accompany Dr. Dolittle to England to earn money for him (in Doctor Dolittle's Circus and Doctor Dolittle's Caravan.) The pushmi-pullyu usually only uses one of its heads to talk, reserving the other for eating (thus allowing it to eat while speaking without being rude) and claims that its great-grandfather was the last unicorn.

In the 1967 film, the pushmi-pullyu was instead portrayed as a double-headed llama. The doctor can immediately speak to the pushmi-pullyu, knowing that llamas speak a dialect of camel language. The Eddie Murphy film has a brief scene where it is walking in the background while Dr. Dolittle talks to the tiger in the cage. This is in keeping with the fact that Murphy's movie version is only loosely based on the books.