I have enjoyed this topic so much, I'm going to give you my all-purpose stopper to both
"Do it again" and "I know how you did that". This bit stops them dead, and has the benefit of being nonconfrontational. The lines suggested earlier might be better saved as comebacks for the particularly insistent.

My solution is the "Cards From Mouth". That's right, the mainly-stage stunt made popular by Karl Malden, ("The Sting II") Jeff McBride and Bill Malone, in which a seemingly endless stream of playing cards comes shooting out of your mouth. Cop a handful off the bottom of the deck, and you've got your all-purpose answer, like this:

"Do that again!"
"Sorry, if I do it again, something bad might happen--you know what might happen? ARRRGH" (the "ARRRGH" is the sound of the cards coming from the mouth)

"How did you do that?"
"If I told you how I did it, something bad might happen..."
OR
"Well, they say something bad will happen if I explain it, but if you really want to know, at the beginning of the trick,..ARRRGH"

These responses all have an air of confidentiality, which tends to bring the victim in close to your face. This sets them up perfectly.

There are some rules I've learned about this trick:

1. It's shocking if done once, but it's only really funny if you do it more than once. They really don't get over the shock until the second time.

2. Most audiences think it's vulgar, but they like it. The ones that are genuinely offended will be too uptight to ask you questions like "Do it again" anyway.

3. Treat it like it's just an annoying cough. Under selling makes this work. I usually go onto a card trick with the line,
"Here, pick a dry one...."

I encourage you all to give it a try. Occasionally, the trick is your best friend. Like the night I did a particularly strong mental effect, and the amazed patron asks, "What are you, Satan?" my response,
"Why, no, actually--ARRRGH"

I think your cards from mouth is the funniest thing! The sound is what makes it so funny. ARghhhhh!


Here is a funny bit I learned from my friend, Jim. It works good with TT silk magic.

Produce the silk so half of it sticks out of your fist. Reach out to the spectator and say " You can touch it, it's real!" As they grab for the silk, pull it away little bits at a time. Don't let them touch it! You will get a good laugh, it really gets them when you say "did you feel it?" They will say no. Then you reply "Not feeling well, I'm sorry!"
It's great! I love it

Try it.

How did you do that!???

Very well thank you.

or

I don't know, but if you find out, will you tell me?

When I have the luxury of sitting at a table at a hospitality suite or corporate party and doing a 10-12 minute set, my pacing is usually good enough that I get little of "do it again." However, "how'd you do that?" comes up often enough. I take it as a complement.

In walk around, where you do 2 or 3 effects and move on, both questions come up often. In the case of "do it again", I use the stock line" you know, I'd have to kill you" or "if you liked that, you'll love this." And move on to another trick.

With "how'd you do that?" I'll say something like: "I KNOW, don't you just LOVE that?" And move on. Or, "it ain't easy." The main thing is that whatever your response, keep it light hearted. Close up magic, as done by most of us, creates laughter. It is important to maintain that sense of fun. A smart mouthed response can throw a wet blanket on all that you have accomplished up to that point. The responses, here, have been great, so I am preaching to the choir, but we have all seen the tension that a terse response can create.

I confess: I have copied a couple of lines, here. Thanks

That's why we're sharing them, right?

There are quite a few real gems here.

I get "how did you do that?" and "do that again" lots. I work in bars and I tell them I'll do it again if you buy me a drink.

What happens with this situation where you show some kids, then they are yelling at their parents or other friends who were not watching to 'come over hear and see this!' (I imagine it happens with adults).

Situation is your specs pull new specs in to see the trick.

When I get asked the usual question how did you do it I use the line mentioned already.....very well! I then follow it up with ....can you keep a secret? When they say yes and their eyes light up thinking they are going to find out say....so can I!!! and walk away.

Seems sorta cruel doesn't it? lol

"We'll meet again, so watch closer N E X T time... "
Got it?

If they want to know how to do a trick tell them to say <insert unpronouncable word here> 5 times fast then you will show them a new trick.

if they want to see it again tell them you would but you forgot how.

those are my favorites

ChessMess

Two suggestions

firstly when parents or friends come over to check out what the fuss is about, just say to the group 'that was nothing, how about this....and lead into a new trick

or secondly, if a group of people are building, and those first there are singing your praises, maybe it's time to 'magically' produce your business card, and gain some bookings.

hope this helps

Do that again!

Response, with age in mind of course:

Ya know, I keep getting that request, but I ran out of viagra last week.

I love this topic. Since it has happened to every one of us. I purchased a pack of "pact with the devil" forms from Burt's Magic Shop and when I get those question I usually pull those out. So far I have had only one pilot from the airline I work for actually sign one. Some people get a laugh from it while other people like, my girlfriend, think I am strange.

Hey, that's a great idea, of course once they sign it, you too have made a verbal contract to reveal the trick, otherwise you could go to **** for not honoring your word. Catch22... Someone is going to **** unless you expose the trick. (Logic taken to the extreme... yes I have no real life today)

Something that gets a laugh for me sometimes, after "Do that again!":

I say, "So you weren't watching, hey?" I pause for a long expectant second so the question isn't rhetorical, and often get a stuttery answer one way or the other. Regardless of the response, I'll follow with "Okaaaay, did you seeeee.....THAT?!" I say "that" quickly and a little louder, and look at them expectantly. I make sure to do ABSOLUTELY NOTHING between "seee...." and "that" except maybe a slight twitch of my head. You can stop here, or regardless of the answer add "Oh, so that's the problem..." This almost always gets a laugh and the request for a repeat is completely forgotten or excused.

-bigwolf {*}

I usually reply "Watch this" and then go straight into my next effect.

Great posts guys! Definitely going to include the lines offered here. Reading the posts got my mind juicing, how about really doing that again? Prime the spec by asking him "are you sure you want me to do that again?" Do a quick trick called "that again", ie figure out a suitable effect that can be named "that again". For starters, cardmen can repeatedly force the spec to choose the same card again and again (using diff techniques of course)... etc. And you end by saying, "There's that trick, "that again"

:righton:

I always like to use one of Greg Wilson's responses to "how did you do that?'..."thank you, I'll take that as a compliment!"

If the person persist to ask to "do it again", I like to respond with "what's wrong? you didn't see it the first time?". Always being lighthearted about it, in a joking manner, usually doesn't lead them to ask again.

Only problem with "didn't see it the first time?" is that older teens my age will blatently lie to you. Good line, though.