If you have a deck where the jokers are identical, you can use them as impromptu duplicates by forcing one of them. I think this has to be handled carefully, though, as most laypeople know that there are two jokers in a deck, so the trick has to be constructed in such a way that duplicates aren't the most obvious method.
I've played around with it a bit, and I find that a good idea is to set up the fact that there's only one joker in the deck a couple of tricks before you're actually going to use it. So, at the beginning of your act, you might say something like, "I'm using a normal deck of fifty-two cards...oh, no sorry, fifty-three, there's a joker in there too...they're not all the same or any nonsense like that," while casually displaying the faces of the cards. Ostensibly, you're just showing that it's a normal deck, and in them accepting that as a fact, they're implicitly accepting the idea that there's only one joker.
