I suppose, although it requires three things: 1) a friend who happens to be flying out of Paris; 2) willingness to take a trip with him to CDG; and 3) willingness on both his and your part to bear the (perhaps infinitessimal) risk that an authority will see your scam and arrest you.

One can also easily cheat paying for metro/train tickets in Paris, but apparently the system generally works because people don't like to hop turnstiles or take the risk the ticket checker will come by.