yes Cherry, "bambino" could be an adjective too BUT
"bambino" ,which generally means child, belongs to human semantic field, while gatto (cat) comes from animal world. It would be strange humanizing a cat!
so we prefer translate it with "piccolo gatto" or "gattino"... =)
I hope this was a good explanation, but if it wasn't I'll try my best to be more accurate!
ciaooo!