I always like to have some very, very quick tricks handy because sometimes if you can make a fast (and good) impression on an otherwise disinterested spectator, you can turn their attentions to you for a longer set of more miraculous effects. I put this trick in that quick trick category. It is fast and visual.
You show two pieces of cardboard, the same size as jumbo playing cards (5x7 inches). They are connected in the center, where a square hole runs through them. Each card has two sides, of course, and one side is red and says OUT on it, and the other side is green and says IN. The cards are connected so that the OUT sides are on the outside, and the IN sides are in the inside. (Makes sense, right?) But after letting the spectator examine the connected cards, you give them a few quick folds, and suddenly the OUT sides are in the inside, and the IN sides are on the outside. Again the spectator can look at the cards -- they are still connected (and in fact, they really do not come apart!) But to set the world right again, you fold the cards a few times and unfold them to show the OUT sides ont he outside and the IN sides on the inside again.
The instructions include a third all white card that is trapped between the In and OUT cards -- the idea is to remove the white card. I personally think this makes the effect too complicated and more like a puzzle than a magic trick. So I recommend doing it without the extra white card. But you get the extra white card in case you find that presentation to be one you like.
When table hopping, I often use this as an opener, because it takes no more than 30 seconds and leaves the spectators profoundly puzzled, and ready to enjoy some magic! Kids love this also, because it is so visual. Just be careful... they will want to tear it apart to find out how it works, so keep it away from grabby hands. :-)
Brand new with instructions