The answer to this question seems to be a rather complicated one. Good job noticing that in Italian adjectives usually follow the noun. :)
Both "una coppia strana" and "una strana coppia" translate to "a strange couple" (http://www.duolingo.com/#!/comment/148697) , but according to the second link (blog.transparent) the meaning is a bit different when the adjective is in front of the noun as opposed to being after the noun.
Check these two helpful links for more information regarding adjectives and their position:
I know I didn't directly answer your question but I hope it helped a bit.