What do you call a baby kangaroo?

A joey, and it is born after about a month at roughly the size of a jellybean - blind, pink, with no hind legs to speak of. It then hauls itself unaided up through its mother's fur to the pouch, using forelimbs that are the only developed part of it, and latches onto a teat which swells in its mouth to hold it there for months.

Marsupials have effectively moved most of gestation outside the body, and the arrangement has some remarkable machinery attached. A female kangaroo can carry a joey at foot, a joey in the pouch, and a fertilised embryo held in suspension waiting for the pouch to clear - and can produce two different kinds of milk simultaneously from adjacent teats, tailored to a newborn and an older sibling.

That paused embryo is a drought strategy. In hard conditions the female can hold development indefinitely and resume when the rain comes, so the population can respond to a good season faster than an animal with a fixed nine-month cycle ever could.