The moment Sarah pressed the button some machine somewhere nearby let out a pulse which fired out really quickly and started messing with everyone's DNA and made changes occur from that DNA change real quick. In turn it made Y-chromosomes turn into X-chromosomes, and in a double X-chromosome relationship one of the X-chromosomes would turn into a Y-chromosome for some reason.
Sarah noticed that he was a bit taller, but besides his height his build didn't change much instead of being a bit more flat.
Paul felt his figure start curving as his breasts started pushing out into C-cups, her hips matching as they flared out with her butt, and her hair elongated to said butt
Samantha's breasts had migrated to the nether regions giving her a fairly sizable lump which ended up breaking through his panties instead of two lumps on his chest. leaving her long dick hanging if it weren't a little hard. Besides that her little pudginess translated into a small gut.
Adam turned into a fairly average girl. Not much of an hourglass figure, but she had a cute figure with B-cups and a cute little bubbly butt. She did notice though that her nipples were a bit large and were really poking through her shirt
Robin fell to the same change Adam did and became a less than above average guy. He did have a little more muscular arms though
Then finally Jonathon changed with her chest swelling to E-cups bursting through her shirt and her hips and butt flared as her waist shrunk making her pants fit weird and then fall to the ground when her hips flared and broke the waist. If she would notice anything though it would be that she resembled the girl that had dumped her.
The little party started to figure out what had happened when.