"Please swear on your testicles. . . ." The word "testis" is derived from Latin and meant "witness" or "spectator." English words "testify" and "testament" were derived from testis. The reason for this derivation is not known. However, it has been proposed that the testes were witnesses to virility. Romans required that a witness be an adult intact male. Prepubertal boys, women or eunachs could not serve as witnesses. Placing a hand on the testicle (or someone else's testicles) was a requirement while testifying in some cultures. Chapter 3 - Male Anatomy

"Some female spiders can be so mean" Some spiders have no penis. They eject sperm from their abdomen onto their web. The male spider picks up the ejaculate with a special set of antennae and searches for a receptive female who produces a pheromone. The male has to be very careful and deposit the semen by surprise because the female will eat him if she catches him. Chapter 9 - The Luteal Phase

"Milk Bar" Infant kangaroos in their mother's pouches nurse from two nipples, and two babies of different ages commonly nurse at the same time. So, the mother kangaroo produces two kinds of milk - on one side, fully rich for the younger and on the other side, a sort of skim for the elder. Chapter 14 - Placentation, Gestation and Parturition