Spend some time asking Google. You will find differing opinions, but my take is that there is no "penalty." There are only supplemental results. Since G wants to show what it believes to be the most relevant content for any given search, it will exclude everything that it considers duplicate from the SERPs for that search.
Try this:
Go to Google.
Change the search settings to display 100 results.
Search for cat fight or any other phrase you like.
Scroll to the bottom, and click 10.
Keep doing this until you get the message at the bottom of the results that says, "In order to show you the most relevant results...blah, blah, blah...you can repeat the search with the omitted results included."
Those omitted results are the mythical duplicate content penalty. The page is still there and indexed in G...it just doesn't show up for that particular search.
You could make your content unique in a number of ways including simply mashing it up on the same page with other content. Say you quote an entire article and write a couple of additional paragraphs about it and include a picture, video, or something else...Boom, unique content. You can even use this to shift the keyword focus of the original content.
The above is simply my opinion, but so far I have a couple of sites where this exact mashup method is getting me rankings for longtail phrases where those pages have zero unique content. For the sake of trying to keep these domains in the index, though, I do have a number of completely unique pages with original articles on them.
Someone may come along and post here that everything I've said is bullshit and wrong, but it is just the ramblings of a relative nOOb in this space so it's worth what you paid for it.
