"Pretentious, moi? Mai, non!"
But seriously French people do exactly the same thing with English expressions, often in much the same way. You will often hear little snippets of Franglais in conversations and especially when talking about music young french people often mix in complete bits of Enlgish.
Makes them sound stupid tho', "Yeah, thats dope" just doesn't have the right ring to it when done with a French accent