Fred was out for a hike, deep in the woods, when he stumbled across an odd looking rock sticking out of the ground. A hurricane, with heavy winds and rain, had swept through the area just a day or two ago and the whole reason Fred was out for a hike was to see the changes to the landscape that the hurricane had wrought. The rock had clearly been unearthed from the rainwater rushing through the area from the surrounding forest, which must be have been why he had never seen it before, despite his occasional treks through this area.
As Fred drew closer to the rock, he noticed that it was actually not a rock but some kind of pillar with ornate carvings on it. An obelisk, if he was using the word correctly. Upon closer inspection, Fred saw that this obelisk was polished stone with a completely unrecognizable language carved deeply into it's surface.
Fred was very excited by the discovery. Surely he had stumbled across some ancient, unknown artifact that would make him rich and famous! His heart was beating wildly as he reached out his hand and touched the cold, smooth surface of the object.
The etchings in the object suddenly emitted a bright green flash of light. Fred reeled backwards, falling onto his ass and yelling in surprise.
"Greetings, mortal."
Fred looked around frantically for the source of the voice. There was no one in sight.
"Who are you?" Fred asked in fear.
"That is of no concern to you," he heard the voice reply. "You are the first human to touch this artifact in thousands of years. As such, I have decided to grant you my boon."
Fred stared in disbelief at the object, his heart racing. "What does that mean?" he asked the disembodied voice.
"I am granting you a special ability, for your amusement as well as my own. From this point on, whenever you touch another person whether casually or intentionally, your genitals shall be swapped with theirs. Only you shall notice this change, every other individual involved will not be aware of this swap. The only way to recover your original genitals will be to swap with the person to whom they are attached with another touch."
Fred felt a stir of desire in his cock. Fred had fantasized about swapping bodies or body parts with other people before, but he never considered that it would ever actually happen in this reality.
"Th....thank you," Fred stammered as his mind attempted to comprehend what was happening.
"You're welcome, mortal. Enjoy this gift. I certainly know that I will." And with those final words, Fred watched in amazement as the obelisk vanished completely, the ground around it collapsing from it's sudden disappearance.
Fred sat on the ground in complete disbelief. Had that actually just happened? Perhaps he had had some kind of stroke or brain aneurysm that caused him to hallucinate. Fred had never experienced something supernatural his entire life, so it's not possible that this suddenly happened out of nowhere, right?
"Hey," Fred heard someone call out behind him, "Are you ok? Do you need help?"
Fred turned around and saw another person standing on the trail behind him.