Katie had her head swapped with Barry's, but with additional changes.
Her young, spry, kissable face and her brunette locks looked very out of place on Barry's tall, strong, hairy, and slightly-pudgy body. It had smelled when the transformation first occurred, but Katie had taken a shower.
That was not the only change though.
Katie's familiar vagina was present in place of Barry's penis, feeling odd in a nest of pubic hair that wasn't originally hers.
In addition, Barry's arms were noticeably different.
Barry's right arm had become large, muscular, and much longer, stretching all the way down to past his, or now Katie's knees. It didn't help that she was right-handed.
Katie had two appendages on her left side. Barry's original arm had tapered and softened, starting at just above the elbow, and turned into a veiny tentacle that ended in the circumcised head of a penis. It had already gotten hard before, and had freaked Katie out with its rigid "salute". With Barry's help, it had finally went flaccid after 10 minutes, and an aroused Katie had finally calmed down.
Below the penis-tentacle was a normal, clearly feminine arm with an extra hand attached to its wrist, facing upwards, parallel to the original hand.