This is a great comedy effect involving audience participation. A little naughty, but not offensive, it makes for a very entertaining magic trick for a grown up audience.
In effect, the performer displays two colored handkerchiefs, which are tied together. Three spectators are invited to participate in the effect, at least one of whom is a lady.
The lady is asked to hold the knot in front of her chest. The ends of the handkerchiefs opposite the knot are held by the other two spectators. The magician asks the spectators to pull the ends of the handkerchiefs at the count of three, claiming the knot will magically vanish.
When the spectators pull the handkerchiefs, the knot has vanished, but tied between them appears a super size brassiere, much to the surprise of the lady. Her natural reaction is bound to have a big impact on any audience.