When you, as an adult, spend the majority of your time creating adorable G-rated worlds for kids, that hidden sexual side of you is bound to come out — and probably, shall we say, enthusiastically. (Anyone remember the movie S.O.B. in which squeaky clean Julie “Mary Poppins” Andrews rips her top off and exposes her boobies? No? Good. It’s scarring.) Well, in their spare time, four Pixar animators have been working on a series of cool art books, the second and most recent of which is “The Ancient Book of Sex and Science” (the first was the now sold-out “Ancient Book of War and Myth”).