Same animals in small, medium and large.
"Macropods are marsupials belonging to the family Macropodidae, which includes kangaroos, wallabies, tree-kangaroos, pademelons, and several others."
"A wallaby is any of about thirty species of macropod (Family Macropodidae). It is an informal designation generally used for any macropod that is smaller than a kangaroo or wallaroo that has not been given some other name."
"A wallaroo is any of three closely related species of moderately large macropod, intermediate in size between the kangaroos and the wallabies."
"A kangaroo is a marsupial from the family Macropodidae (macropods, meaning 'large foot'). In common use the term is used to describe the largest species from this family, the Red Kangaroo, the Antilopine Kangaroo, and the Eastern and Western Grey Kangaroo of the Macropus genus."
More on Wallabies
http://www.youtube.com/watch?v=rBIk3VIMd_M
(that isn't me)