WHAT IS THE ADULT NAME for A BABY ANIMAL CALLED A JOEY?

Ok, so me and my roomie had a discussion about this earlier i told him it was a kangaroo i know this because my 2nd grade gym teacher used to call me a joey because i would put my hands in my pockets and jump around. HE claims that because he has been to australia, he knows that Joey's can refer to any marsupial, primarily the koala bear. now i know a simple google can fix this but i want someone to tell me im right.