So  Vesryn invented a ray gun that turns people into something of their opposite. ...and alas for Tracy and Alicia, they happened to be standing around at the moment it needed testing.

At first the two girls were surprised, and had the distinct feeling they SHOULD be upset by the impromptu change... But Tracy just can't get over how good it feels to be so big and strong, and Alicia can't muster up the annoyance she knows she ought to be feeling, in favor of marvelling at her new, hyper-feminine figure.
Thoroughly under the sway of their transformations, it appears they're at  vesryn 's mercy as to when, or if, they'll be changed back :o