"Yes, miss, you. Come forwards to the stage," said the Madame Illusia.
A girl of no more than nineteen squeals and begins to force her way to the front of the crowd, grinning madly. She's reacting almost as if she's won some kind of fantastical award. Clambering on to the stage, she is regarded by the crowd, and indeed the Madame. She is quite a nubile young lady, seemingly the female counterpart to Randy. A generous bosom, thin, long legs, with clothes that hug to her body, showing off how painstakingly thin she is. Brandishing a smile, it is obvious to anyone with even a small facet of sense that she adores the attention. So that's why she so readily volunteered herself.
"Tell us a little about yourself," said the Madame.
"Well, my name is Charlotte, I'm a virgo, and my breasts are a D cup!" she squeals excitedly.
The Madame Illusia simply smiles serenely, having seen this sort of person her whole life, and knowing that they made the best specimins for her show.
"Well, I suppose I should continue," said the Madame, clapping her hands.
At once both Randy and Charlotte stand bolt upright, as if constricted by some invisible force. They look almost inanimate; like mannequins. It's now that the Madame murmurs some kind of incantation, and the two of them begin to undergo some peculiar changes.
Purple smoke begins to swirl around their feet, but it's still obvious what is happening. Their skins seem to be crawling, almost melting around them as their features succumb to opposite alterations. As her chest deflates, his inflates, and as his shoulders narrow, hers broaden. His face begins to soften, and hers develops more rugged contours; stubble. Their legs essentially swap: hers growing hair and becoming stocky and muscled; his losing hair and thinning, becoming sensual.
By now the purple smoke has shrouded them from view, but amidst all that, it's clear from the commotion in the crowd that they know what they have witnessed. All they want is for the purple veil to lift and to see the responses from the changees.
And thinning out, the mist does indeed lift, and clapping her hands, the Madame resumes control of their bodies back to them. Just not as they left them.