Your performing on the streets, when you stop a couple. You introduce yourself and show them a great magic trick. Just as the trick is ending someone walking by notices and ask ,"Can you do that again?" Of course you cant, because some tricks you just cant show twice without setup (and the general rule "never show the same trick twice".
How do you get out of that situation smoothly without just stating no? I feel like if i just say no, the trick looses a little bit of its mystery, because the audiance knows that i probably set it up....... Well maybe its just me that feels that way. But how do you guys get out of that situation?
You could also be ready with a new trick. When they say, can you do that again, respond...
"Yes, but I would rather entertain you with a new trick that you have never seen than something you have already seen. Let me show you this one..." Go into the next affect.
"I am sorry, I never repeat a trick for the same audience. My policy is "Once is entertaining... twice it educational" (Say it with a smirk)... it get's good results.